Our explanation will be centered in the second formula, which implies and explains the other two by its own absolute evidence.

Simultaneity of affirmation and negation is impossible. We never inwardly experience affirmation and negation simultaneously, although we can express such simultaneity in language. But reflection upon this lack of experience immediately shows us its subjective and objective impossibility. The subjective impossibility springs from the fact that affirmation and negation are two opposed acts of the same intellect, which is their source and their subject. These acts are two spiritual accidents of an intellectual substance, two accidents of which one is the negation of the other, just as, for the eye, black is the negation of white; so it is impossible that they coexist simultaneously in the same subject. Now, est is the soul of every affirmation, just as non-est is the soul of every negation, and these two verbs are two diametrically opposed acts of our intellect. But in order that two distinct acts be able to coexist in the same subject, they must be unified, arranged in hierarchy, one must be the cause of the other; thus, the intellect is the act of the soul that is itself the act of the body, but the soul is the source of our intellective power. In the same way, a habit and the act of a habit are simultaneous acts of a power, but the power is their cause. However, affirmation is not the source of negation but is its contrary, in the sense that one expels the other, puts it out. Translating affirmation and negation into the verbs they express immediately reveals their opposition. For the mind to be able to seize these two opposites simultaneously, it would have to unify est and non-est, therefore, be able to judge that est is non-est; but in this judgment the predicate is opposed to the subject just as non-ens is opposed to ens in the ontological aspect of the principle of non-contradiction. Thus, simultaneity of affirmation and negation amounts to negation of the principle of non-contradiction, which we have shown to be unthinkable.

The objective impossibility of simultaneous affirmation and negation has a source other than the one we have just discussed, and it arises from the necessary exclusion of two contrary acts in a same subject and under the same aspect; it rests upon the respective objects of affirmation and negation, on their specification by the outer real. Let us examine the affirmation and negation of being in the two following formulae: being is being; being is not being. The terms of the two propositions are identical; being has the function of subject and predicate in both enunciations. Now, for the mind to be able to think affirmation and negation simultaneously it would have to be able to identify being and non-being. For to say that being is not being is the same as affirming that being is non-being, which is counter to the ontological principle of non-contradiction. Therefore, the objective impossibility of simultaneous affirmation and negation rests ultimately upon the impossibility of identifying being and non-being—the two hypotheses are absurd or unthinkable for the mind.

As to the third proposition, frequently called the principle of excluded middle or excluded third, it is merely the logical consequence of the absurdity implied in a simultaneous yes and no about the same thing considered from the same aspect. This consequence will be briefly explained in our study of the opposition between truth and falsity in contradictories, which is the topic of the following paragraph.

(c) Epistemological aspects of the principle of non-contradiction. In our analysis of truth we have said that truth exists formally neither in the exterior term of judicative activity, nor in the act of judgment itself, but in its immanent term, enunciation. Having considered contradictory opposition in the object of knowledge or being, and then in the act of judgment, we must now consider the role of this opposition in the characteristics of enunciation as measured by being, i.e., in its truth or falsity. Two questions arise about this subject, and they may be stated as follows: Can two contradictory statements be simultaneously true or false? Or, on the contrary, must one be necessarily true if the other is false, and vice versa? The answer to these two questions constitutes the epistemological study of the princple of contradiction.

It is impossible that contradictory statements be simultaneously true. This affirmation remains obscure as long as it is not illumined by the previously explained doctrine concerning the complexity of human truth (which is a relation of measured to measure between the intellect and reality) as well as by the nature of contradictory opposition. Upon the absolute comprehension of these two doctrinal points rests the evidence of the absolute incompossibility of the truth of contradictories. As we have seen, truth taken formally belongs neither to reality taken absolutely nor to the intellect considered in itself, but is the result of a bond established by judicative operation between the fragmentary aspects known about reality and the ontological unity of this same reality. There is no truth without enunciation and no enunciation without the complex act of the mind’s referring to an equally complex reality by which it is admittedly measured. Therefore, when we examine a truth, our object is always made up of a mental activity and the thing which is its term and measure. But contradictory opposition between two propositions is always made up of two mental acts, yes and no, respectively concerned with the identity and nonidentity of being and nothingness. Consequently, if the identification of being and nothingness plunges the intellect into absurdity, and if simultaneity of yes and no begets the same absurdity, then simultaneously true contradictories involve the same absurdity, since the truth of a proposition depends upon the mental act and the object by which it is measured.

If one contradictory is true, the other is necessarily false. We have seen that there can be no intermediary between being and nothingness because one is the absolute negation of the other; nor can there be any intermediary between yes and no, because yes deals with the identity of being with itself, whereas no denies the identification of being with nothingness. But being essentially constituted by the absolute character of yes and no, and of the being that is its object, the truth of a contradictory cannot admit an intermediary, any more than its constitutive elements can. Therefore, the principle of the excluded middle, inevitable consequence of the opposition between being and nothingness, between yes and no, also excludes with like inevitability the possibility of an intermediary between the truth and falsity of contradictories. Whence the principle so often repeated by philosophers: Whatever the subject, either its affirmation or its negation is true. Hence, if one of them is true, the other is inevitably false.

Among our contemporaries this epistemological aspect of the principle of contradiction is most frequently called the principle of raison d’être, or sufficient reason, an expression found in neither Aristotle nor St. Thomas, although both of them were in possession of the primary evidence hidden behind these expressions. They expressed this first evidence in terms of convertibility between being and the intelligible: eadem est dispositio rei in esse et in veritate. If, indeed, being and the intelligible are proportional, non-being and the unintelligible are also. But the principle of raison d’être, or sufficient reason, is nothing but the thing’s capacity to account for itself to human reason, to reveal its luminosity, to be intelligible and understood. But truth is nothing but judicative knowledge as vindicated, guaranteed by the intelligibility or the unity of the being with which this activity is concerned. Now, two contradictories are characterized by the fact that one is concerned with being and the other with its negation; therefore, one deals with the intelligible and the other with the unintelligible. However, the unintelligible has no raison d’être, guarantees nothing, therefore is the foundation for no truth, however small. Consequently, if one of these contradictories is true, the other must necessarily be false.

This analysis, at once too succinct and too long, has shown us the role of the primary object of the intellect in its natural acts, of which truth is the inevitable term. Being is always present under very different modalities according to the case, but it cannot not be present, for otherwise judicative activity would wholly disappear from the human soul. This activity, which composes and divides concepts, is itself subject to the law of contradiction, and its term, enunciation, is also determined, in its truth or falsity, by the presence or absence of being, the first and constant concern of every human intellect. Thus, the principle of non-contradiction embraces a trinity of correlative fields: that of being, of affirmation of being, and of the truth of this affirmation. Now we shall see that it underlies all other dignitates or first principles, which depend upon it to give the intellect immediate evidence, the object of which is more limited than its own, despite its transcendental character.

2. The Principle of Identity. Since the advent of Kantianism and the tyrannical rule of mathematical knowledge over contemporary science, the principle of identity has been much discussed. It has either been given primacy over the principle of non-contradiction, or been reduced to nothing by emphasizing its tautological character, or been denied all real value and granted only a formal value directing the mechanism of the mind completely cut off from the real. This overvaluation and devaluation of the principle of identity are both rooted in common ground, the arid and sterile ground of philosophical idealism. For, by denying that concrete and existential being is the starting point for philosophical reflection, the mind has locked itself within logical frames that have held and will hold it prisoner until the day when a right and, therefore, humble view of human nature will make it understood that we are “below the angels but above the beast,” that we do not create our concepts or possess them at birth, but that neither are we condemned to an animal empiricism in the order of knowledge. In the context of realist philosophy, the principle of identity has kept its value as evidence and as concrete truth, but under the domination of the principle of non-contradiction, of which it is a sort of contraction or specialization. First, let us look at its ontological sense and then at its epistemological meaning, or the truth it conveys.

(a) Ontological aspect of the-principle of identity. Here are the different ways of stating the principle of identity: everything is identical with itself; being is being; every being is necessarily what it is; being and one are convertible. To see how these different formulae are equivalent, we must necessarily recall to mind the notion of identity whose strict meaning is nothing but the unity of a being with itself.

Identity is unity or union: either the things which are said to be identical are many as to their existence, and their identity comes from the common possession of one element; or there really is unity as to their existence, but the intellect uses this unity as a plurality in order to conceive a certain relation; this is the case when we say that a thing is identical with itself... but this relation of identity is not real but is only a relation of reason, and it is according to this relation that a thing is said to be identical with itself, absolutely. [In V Metaph., lect. 11, n. 912]

Since the principle of identity is nothing but the affirmation by the intellect of the unity of being with itself, to speak of unity is to speak of the intrinsic non-division of the real and its division from all else that is not itself.

One does not add any reality to being but only the negation of division; for one means undivided being. This is the very reason why one is convertible with being. For every being is either simple or composite. But what is simple is undivided both actually and potentially; whereas what is composite has not being while its parts are divided but only after they make up and compose it. Hence it is manifest that the being of anything consists in indivision; and hence it is that everything guards its unity as it guards its being. [S.Th. I, 11, 1]

We are now in a position to understand the different formulae used to express the evidence of the principle of identity.

Everything is identical with itself. We know that being as such has five properties or general modes which the mind discovers by deeper study of its nature. The first of these properties is being as res, i.e., as endowed with a quiddity that determines it and gives it a stability that the act of existing by itself does not possess; these are, in a way, the special and stable riches that everything possesses as its own because it is constituted by a nature or specific quiddity which makes it to be itself, that is, intrinsically undivided and externally divided or opposed to all that is not itself. But from the fact that being as res has a special type which characterizes it internally and divides it from everything that is not itself, it is unum et aliquid, one and something, which is precisely the notion of identity.

Now let us consider the formula of the principle of identity. It is made up of the subject of a verb and a predicate. The subject is every being as quiddity or res; the predicate is every being as undivided in itself (unum) and divided from all others (aliquid). But it is the same reality that is ens, res, unum, and aliquid, a reality which the human intellect considers as a plurality by virtue of the weakness of its hold on the real and the fragmentary and the abstractive character of its cognitional procedure. Thus, there are many concepts but an absolute oneness of the thing designated by these concepts. In this judgment of identity the intellect does nothing but measure the multitude of its concepts of being by the concrete unity of the latter, and that is the whole ontological significance of the principle of identity. There is no tautology here but an explanation, for our intellect, of the interior and typical riches of every being, riches that make it a mirror reflecting something of the infinite opulence of the creator, while at the same time they enable it to hold a precise place among the indefinite multitude of the other beings surrounding it.

Being is being. This statement of the principle of identity, whose transposition into mathematical language seems like pure tautology, means nothing of the kind in metaphysical language, for the meaning of the being-subject is entirely different from that of the being-predicate. Indeed, the being-subject is a name expressing the substance of the being itself, therefore, of that which is composed of essence and existence; whereas the being-predicate is actually a qualifier, a determination grasped by the mind as a property of being, a determination making it to be itself, internally determined, undivided, and opposed to everything that is not its own substance, i.e., this essence and existential act characterizing it. This, in turn, comes back to the first formula that every being is res, unum, aliquid, or every being is identical with itself.

(b) Epistemological aspect of the principle of identity. In the preceding paragraph the human intellect perceived being and its ontological capital; here it is the truth of the enunciation, term of mental activity, that we shall analyze. Reflecting on this concept, which is the fruit of a judicative act, man cannot help observing that the bond uniting subject to predicate, i.e., being and its absolute unity, is a necessary bond whose rupture would inevitably entail loss of intelligibility to the real. Here we enter the field of the per se proposition, characterized by the causal link binding predicate to subject, whether this predicate be essential or accidental. This doctrine of predicates per se as opposed to predicates per accidens is the basis for a division of propositions which we have already met in studying judgment. Actually, this kind of proposition, called modal, is a judgment of judgment whose immediate object is not the thing but the truth of our knowledge of the thing; it is a sort of value judgment on the truth of our knowledge, a judgment expressed by the phrases, it is impossible, it is necessary, it is possible, it is contingent.

Reflecting upon this proposition—every being is being, or every being is identical with itself, or every being is one, i.e., interiorly undivided at the same time that it is divided from everything else—the intellect cannot fail to see that the link uniting the predicate to the subject is a necessary link, immobile, and, in a certain way, eternal, transcending time and the intellects that think it. This unification made by the mind between two concepts inseparable from each other and measured by one single and same thing considered as double by a trick of our intellect—this unification conveys an infallible truth to which we cannot not adhere. It is then that the mind utters its value judgment: it is impossible that being not be identical with itself; or, again, it is necessary that being be undivided in itself and divided from everything else; or this other affirmation—it is necessary that being and one be convertible.

In this modal judgment on the principle of identity, we perceive the same laws of our intellect’s imperfection in regard to the real on which it must feed. We cannot think the truth of being without opposing it to nothingness, which is its negation; in the same way, we cannot think the truth of the identity of being with itself without conceiving it as a negation of interior division without which it neither exists nor is intelligible. This identity of being with itself and its affirmation by the mind beget a truth whose analogy is as flexible as that of the principle of contradiction, for the modes of identity of things flow from their being, whose diversity is indefinite.

By comparing the truth of the principle of contradiction with that of the principle of identity, we quickly discover that they are complementary; for—in that it is repugnant to being to be identified with non-being, which expresses the truth of the principle of contradiction—being must be identical with itself, which constitutes the truth of the principle of identity. It could be said that, for an intuitive intelligence, the truth of the principle of identity would precede that of the principle of contradiction, because intuitive vision of being would reveal its existential actuality determined by a positive quiddity whose interior, indivisible, and undivided riches would, in a way, exaggerate it and oppose it to everything else. But our abstractive mind, whose feeble light fragments the real and can unify it only by the intermediation of many comparisons, first grasps being as actuality in its opposition to what it is not, in order to be able, thereafter, to exploit its interior riches and to perceive it in the unity of its quiddity, lose determination limits and distinguishes it from all the other quiddities surrounding it and which it is not. That is why the truth of the principle of identity can be defended by the truth of the principle of contradiction, but the inverse is not possible; he who in words would deny the principle of identity can be reduced to the absurd. Indeed, if being is not being, it is non-being, and if being is non-being, the principle of contradiction is false; but if the principle of contradiction is false, the human intellect is consigned to total absurdity, to the absolute inability to conceive anything whatsoever: every thought is unthinkable.

3. The Principle of Causality. With this principle we have reached the last group of axioms we listed above, axioms that do not have the same universality as those we have just studied, or the same function in human knowledge. For the principles of causality and of finality that make up this last group of axioms are directly concerned with being in process of becoming, which is the first and characteristic object of the human intellect, being from which, by means of these two principles, we can go right back to the existence and intelligibility of realities surpassing the usual and immediate horizons of our reason. The most general and also the most comprehensive statement of this principle is: Everything contingent is caused. Actually, this general statement applies to three domains: 1) that of physical motion, in which the principle is stated thus: Everything moved is moved by another; 2) that of efficiency, and the principle here is stated in this way: Every efficient action, which is a passage from potency to act, is caused; 3) that of existence, where we have the third statement: Everything that is not its own act of existing is caused.

Perception of the essential contingency of the movement, efficiency, and existence in which the proper object of our intellect is immersed—such is the springboard we use to surpass this proper object and to ascend to the invisible and transcendent causes of motion, efficiency, and existence. Such is the immense domain of the principle of causality. In analyzing it, we shall concentrate upon the notion of contingency and cause that are the key by which we may penetrate the twilight wherein dwells being in process of becoming and the pure luminosity where being abides.

(a) Ontological aspect of the principle of causality. Examination of the subject and predicate of the principle of causality reveals that the thing as contingent has the role of subject and the thing as cause the role of predicate. Now, even superficial reflection upon the notion of contingency compels the mind to recognize that this notion is unintelligible without the notion of cause and, consequently, that the existence of the contingent demands the existence of a cause. A word of explanation about these two notions will show us their correlation.

Being as contingent. Contingent comes from cum-tangere, that which touches upon, whence the nautical term for landing: to touch on shore. The contingent is what happens, what has not always been and, consequently, what can not-be. The philosophical meaning is grafted upon this primary meaning and is expressed by the following formulae: that which can be other than it is; that which can not-exist. The notion of mutability adequately expresses that of contingence, whether it be contingence of movement, substances, or existence, and is irreducibly opposed to necessity, whose etymological origins express immobility in place—a local meaning to which has been added the philosophical sense of immobility or impossibility of being otherwise, unchangeable, immutable.

Hence, the subject of the principle of causality is being as mutable and changing, either because it is movement or change, or because its activity can not-be, or because its existence is immersed in becoming and doomed to vanish. The contingent is not only opposed to the necessary, for there is necessity in the contingent; it is opposed to act inasmuch as act is autonomous, not derived, not received from another, which is to say, divine. That is why the properties of essences are filed under the heading of necessity, immutability, and a certain eternity—if that means anything—but contingency effects the existing of all these essences and their properties because what they are and what they have, they are and have because they receive it actually and without the possibility of discontinuity. This is the reason that contingency is found first and foremost in the act of existing, because its deficient and defective character distinguishes us from Him Who is His own Existere, from Him whose metaphysical proletariat we are, always awaiting and receiving from Him our existential salary. Until we have perceived this first root of contingency, the principle of causality remains unintelligible.

Being as caused. The etymology of the word causa cannot be historically determined, but its philosophical meanings can be reduced to four, two of which express the thing in its intrinsic constitutive elements, matter and form, while the other two express the origin and orientation of being and its different activities, the efficient and final causes. The notion basic to the idea of cause is always dependence; there is no cause unless there is a plurality of beings or a plurality of principles of beings between which there is a bond of dependence. The interdependence of the constitutive principles of a being constitutes the intrinsic causes when it is a question of the quiddity of a composite being, and essence and existence when it is a question of created being. The principle of causality does not apply to this type of dependence, unless the principle of sufficient reason be included within the principle of causality. It is primarily in the field of efficiency and finality, therefore, in what is commonly called extrinsic causes, that the principle of causality exerts its influence and is used by the intellect to explain phenomena, proper accidents, and the contingency of things in the order of existing.

Consequently when we speak of being as caused, we mean the real as dependent upon something which is not itself, i.e., which does not belong to its own interior wealth, which it does not possess, but by which, we might say, it is possessed and from which it continually receives, insofar as it is caused. Since causality can be exerted in the realm of physical becoming, in the realm of metaphysical becoming or of the passage from potency to act in the order of efficiency, and, finally, in the realm of existing or of the creation and preservation of being—the principle of causality applies to all movement and mutation properly so called, to everything that is created being and operation or efficiency.

Trying now to rethink the principle of causality with the help of the notions of contingency and cause as we have explained them, we see its concrete meaning thus: Every contingent thing—every being in process of physical or metaphysical becoming and every being that is not its own existere but has its existere—depends upon another for its becoming and existing. Now, to depend upon another is, in a way, to be possessed by this other, to be its property, to share in what belongs properly to that other without having any claim to independence within this participation. To depend on another, in a context of contingency, is to have a borrowed being and a borrowed efficiency. But that is just the case with caused being, movement, and efficiency. To say that everything contingent is caused is to affirm immediate and per se evidence, for caused being is intrinsically contained in contingent being; without each other they are unintelligible. Whether contingent being is the thing in its physical or metaphysical becoming, whether it is being according to its created mode—this does not in any way affect the evidence and perseity of the principle of causality, because contingency is always fundamentally the same: every being that receives from or participates in another neither is nor is intelligible, except in relation to that other, i.e., to its cause.

(b) Epistemological aspect of the principle of causality. Like every truth, the truth of the proposition affirming the principle of causality depends upon the measurement of that proposition—the concept produced by our second mental operation—by the real in which it terminates. Reflection upon the truth of the principle of causality enables us to make a value judgment or modal judgment qualifying the nature of the bond unifying the predicate to the subject. As we have just seen, this bond is essential, since the notion of contingency is defined by the fact of its causal dependence; therefore, to try to conceive contingency outside its relation to its explanatory cause is as ridiculous as to try to square a circle. When the mind reflects upon the principle of causality, it cannot not see the necessity of its truth, which may be stated as follows: it is necessary that everything contingent be caused; or, rather, it is impossible that everything contingent not be caused, for the contingent needs a cause just as potency needs act.

A second proof of the necessity of this truth can be made by confronting it with the truth of the principle of non-contradiction. Indeed, if the truth of the principle of causality is not necessary, then we can say: Everything contingent is not necessarily caused; but if everything contingent is not necessarily caused, what is essentially potency is not necessarily potency; but if what is potency is not necessarily potency, non-act is act, for potency is synonymous with non-act; but if non-act is act, then non-being is being, which is to deny the truth of the principle of non-contradiction. Thus, we must admit that to deny the necessity of the truth of the principle of causality is equivalent to denying the truth of the principle of non-contradiction, which is impossible because it is absurd and unthinkable.

4. The Principle of Finality: Every Agent Acts for an End. The study of this principle brings us to one of the most important aspects of philosophical thought, because it marks, in a sense, the crowning point of the order on which metaphysics feeds and the blossoming of the knowledge of order by which epistemology is defined. In positing the epistemological problem as formulated by Thomas Aquinas, we saw the importance of order and of the idea of finality. It is by means of the principle of finality that the great metaphysical and epistemological theses are discovered and their solutions investigated and made evident to our reason. In a few pages we shall try to show the immediate evidence and necessity of this principle.

(a) Ontological aspect of the principle of finality. Translating the terms in the principle of finality into the ontological vocabulary gives us the following statement: Being as agent is finalized. We shall analyze the subject and predicate of this proposition in order to discover its precise meaning.

Being as agent. The being in question here is not being as contingency, potency, or recipient, but its correlative, being as dynamism or second act. Actually, agent being is everything insofar as it gives of its superabundance, insofar as it overflows with interior riches which it communicates to others. The word agent must be taken in its widest and deepest meaning, which includes not only the efficient cause whose effect is exterior to itself, but also every immanent causality expressing and revealing its ontological superabundance by an effusion of interior fruits that are both its wealth and the sign of its perfection. Thus understood, the word agent designates not only physical causes but also and especially living things in this psychological activity which is peculiar to them and of which the fruits of knowledge and love are the most typical and richest effects.

Our experience of the agent being, like ourexperience of being as such, shows us action (agere) as a quest, a desire for perfection, a passing from potency to act, and that is, indeed, the physical and human mode of action that we recognize as a means of acquiring a desired and unpossessed good. However, closer analysis quickly shows us that the agent as such excludes this imperfection, this potentiality revealed by desire for what we are not, yet which appears to us as our perfection.

I answer that it is in the nature of every act to communicate itself as far as possible. Wherefor every agent acts forasmuch as it is in act: while to act is nothing else than to communicate as far as possible that whereby the agent is in act. [De potentia, 2, 1]

In the ordinary meaning of the word, then, to be an agent is to be in second act; but to be in second act excludes potentiality or imperfection, at least from the aspect in which the being is in second act, i.e., insofar as it is formally an agent. Every agent, as such, is thus perfect, and its perfection is proportional to the intensity of its act. This is true to such a degree that the absolute agent is at the same time absolute perfection. The real definition of agent being is therefore being insofar as it is perfect or in second act.

Being as finalized. The predicate of the principle of finality is the expression, acts for an end. What does this mean in a metaphysical context? Here is the Thomistic meaning:

One acts for an end in two ways: either for the end of the work or for the end of the worker. The end of the work is that to which the agent directs his work, and is called the why of the work. The end of the workman is that which directs the latter’s intention; which is why, whereas the end of the work can be in another, the end of the worker is always in himself... But action for the end of the worker is of two modes: either by desire for the end, or by love of the end. For the object of desire is a thing not yet possessed, but the object of love is a possession... which is the reason why every creature acts through desire of the end because every creature receives from another its good, which it does not possess by itself; whereas it belongs to God to act through love of the end, because nothing can be added to His perfection. [In II Sent., 1, 2, 1]

To act for an end, the predicate of the principle of finality can thus have two meanings, one of which implies imperfection because it is synonymous with absence or lack, whereas the other is identical with absolute perfection because it means nothing but the act of giving with absolute gratuitousness and disinterestedness. However, in both cases there is a gift, the first being the effect of a received act, and the second the pure outgoing of an actuality so great that it overflows into effects that are like the explosive blossoming of an irrepressible interior fruitfulness. Therefore, we can express action for an end by the verb to give oneself, to communicate.

Reconsidering the principle of finality in light of the data we have discovered by analyzing the terms composing it, we arrive at the following formulae: every being that is perfect or in second act is self-giving; every perfect being is love, therefore, self-communicating, which comes back to the formula of Dionysius; the good is self-diffusive, diffusing itself either by instilling an appetite for itself in imperfect beings or by producing actually participated perfections, as does substance with respect to accidents, universal causes with respect to particular beings, and the Creator with regard to every creature. Such is the ontological meaning of the principle of finality.

(b) Epistemological aspect of the principle of finality. Like the other principles we have studied, the principle of finality is formulated epistemologically as a value judgment or a modal judgment bearing directly upon the truth of the proposition of finality, and indirectly upon being and its perfection. Here are some of the various ways of stating this principle, all of which have the same identical meaning despite their variety of expression, because they all reveal the immediately evident character of the truth of this principle: it is necessary that every agent act in virtue of an end; it is necessary that actuality communicate actuality; it is impossible that being as perfect communicate anything but perfection; it is impossible that perfect being act in view of a non-good or not be finalized.

Whatever formulation is adopted, the necessity of its truth is easily perceived and controlled as soon as it is reduced to the principle of non-contradiction. Indeed, to say that it is not necessary that an agent act in view of an end amounts to affirming that it is possible that being be non-being. As we have seen, the word agent means the thing as actual or perfect, and the term end also means the real as perfection. But existing is the ultimate perfection of every being, and the degree of a being’s perfection is proportionate to the degree of its existing. If, therefore, a thing is an agent insofar as it is, and if a thing is an end insofar as it is being, to say that it is not necessary that an agent act for an end is the same as saying that perfect being is not perfect being, which is counter to the principle of identity, and what denies the principle of identity destroys the truth of the principle of non-contradiction. Thus, it is impossible that the truth of the principle of finality not be necessary and immediate or self-evident, as soon as its terms are perceived by the human intellect. To deny it is to accept absurdity as a law of the mind, which is impossible without knowledge of the intelligible; for the absurd is intelligible only by negation of intelligibility, just as nothingness is knowable only as a negation of being.

Conclusion on the Discovery of Enunciations

We have tried to discover the existence of certain truths which our intellect cannot not perceive, not by means of a method that is the fruit of the intellect’s effort and ingenuity, but by a natural and, in some way, instinctive power that Divine Wisdom has instilled in the intellect, making it a knowing power. Having discovered these truths, we tried to list those which are within the grasp of every man without any kind of philosophical or technical preparation.

Then we showed how these primary truths are resolvable into the very first notions grasped by the human intellect, those of being, quiddity, unity, truth, and goodness or perfection. We should like now to pursue our epistemological analysis, not from the point of view of the object or of the truth the intellect grasps, as we have just done, but from the point of view of the intellectual act by which these first truths are grasped, in order that we may perceive the particular nature and properties flowing from that act. This will be our goal in the next chapter.

CHAPTER 11
ASSENT OR VALUE JUDGMENT ABOUT THE TRUTH OF FIRST PRINCIPLES

Throughout our analysis of first principles we have distinguished between the ontological aspect of these principles, that is, the realism of the terms of which propositions are constructed, and the epistemological aspect of these same first principles, or their truth value. Now it remains for us to determine the nature of this judgment of judgment whose immediate object is the truth of the proposition, or, better, a property of our knowledge and not a property of the real. Here, we are not interested in our knowledge of the existence of truth, which knowledge results from simple reflection upon the various steps in our discernment of the real, but rather in that inner perception of truth whose fruit is an explicit or non-explicit modal judgment proclaiming and guaranteeing that the truths whereby the intellect is enriched have a stability which neither time, space, nor circumstance can shake. In fact, our purpose here is to answer the question asked at the end of Chapter 9, “How do we know the hierarchy of truth?” for the hierarchy of truth is possible only when the different modes of the ratio veritatis have been perceived and compared. But it is impossible to criticize the different modes of truth without studying the intellectual act that is their immanent and conscious instrument; therefore, it is necessary to study the reflex act which is concerned with the nature of truths and which judges their intrinsic value as well as their relations to each other. Since this act is called assent in the philosophical vocabulary of St Thomas Aquinas, we shall examine the description he gives of it as well as the characteristics he attributes to this very distinctive mental act. This chapter will therefore be divided into two sections, the first analyzing the nature of the act of assent, the second studying its essential property, certitude.

Section I: Nature of the Act of Assent

Just as St. Thomas uses the notion of object constantly without making a separate studyof it, he also uses the notion of assent in his philosophical and theological treatises, in dealing with problems of knowledge, without ever elaborating upon its general theory. He is content to describe the nature of this act here and there, dividing it more or less strictly, while applying it to problems raised by the meeting of philosophy and Christian faith. Consequently, explanations of the nature of this intellectual act and its proper object must be picked up where they are scattered throughout his works. Our study of the nature and properties of this act of assent will be organized in terms of the notion of object and act that are always the axis around which turn the essential aspects of our immanent activity.

A. Object of the act of assent

The word assent is given different meanings by St. Thomas in different contexts. Sometimes he gives it the completely general and popular meaning of agreeing with someone, of sympathizing with a way of thinking, of acceding to a request; but usually he gives it a definite technical sense, and then its object is the true as infallible.

The object of the intellect is the true whereas the object of the will is the good. Now there is a certain kind of truth which exludes even the appearance of falsity, as may be seen in the evidence of first principles which the intellect cannot escape without by that fact assenting to them. There is also a kind of falsity which excludes every appearance of truth, and to which the intellect can in no way assent. [In II Sent., 25, 2, 2, sol.]

The object of assent is truth as seen by the intellect to be infallible, undeniable, and secure from every possibility of mitigation by error. Where is such truth to be found? It can only be found in the propositions formed by the intellect, since truth exists formally only in the concept of the second mental operation and assent cannot deal with the ontological truth of the concepts of the mind’s first operation.

It is clear from what has just been said that assent is not to be found in that operation of the understanding by which it forms the simple quiddities of things, for there is no truth or falsity there. For we are not said to assent to anything unless we hold it as true. [De veritate, 14, 1]

This determination of the proper object of assent leads to the conclusion that assent is impossible as long as its object does not exist within us. And since truth as such exists only as the effect of the second operation of the mind, whose concept or enunciation necessarily conveys either truth or falsity, it is impossible that assent exist without the pre-existence of a direct judgment of the intellect. Neither is it enough that intellectual judgment dealing directly with things exist and be true in order for assent to possess its object; the intellect must also perceive the truth of the term of this judgment, must know the adequation of the proposition with the being of the thing. In other words, the truth must be apprehended as existing before assent can find its object.

Since the reason acts reflexively, hence, just as it directs the acts of other powers, so it can direct its own act. Consequently its act can be commanded. But we must take note that the act of reason may be considered in two ways: first as to the exercise of the act... secondly as to the object, in respect of which two acts of the reason have to be noticed. One is the act whereby it apprehends the truth about something.... The other act of the reason is that by which it assents to what it apprehends. [S.Th., I-II, 17, 6]

Since assent has to do only with formal truth, it is evident that the expression it assents to what it apprehends can only mean a truth formally apprehended as existing by the intellect, a truth which becomes an object of reflection and which the intellect judges to be true by the act of assent. Not every truth compels assent, but only those truths whose evidence is such that the mind cannot not grasp them, i.e., the truth of per se propositions.

In order that a proposition be true it suffices that the predicate agree with the subject in some way. But in order that a proposition be true per so the predicate must agree with the subject by reason of the form of the subject. [In III Sent., 11, 4, ad 6]

Every time the human intellect is presented with a truth whose structure is such that identification or denial of identification of the predicate and the subject depends upon the essential constituents of the subject, assent is necessary and inevitable to the same measure that the terms are understood. But when this identification or denial of identification rests on an observed fact and not on essential factors, then the mind can apprehend the truth of the fact and say, “This is so,” but it cannot assent or affirm, “It is necessary that this be so.” The only value judgment it can bring to bear on such a truth is a possible judgment based upon the fact thus, “Since some men are white, it is possible that man be white.” But only the truth of first principles and the truths whose evidence and necessity can be reduced to those of first principles enjoy this cogency and necessitate assent.

There exists a certain truth which is known by itself: this is the truth of indernonstrable principles to which the intellect must necessarily assent. There also exist truths which are not known by themselves but through other truths. This kind of truth is two-fold: some flow necessarily from principles in such wise that they cannot be false as long as the principle remains true: of this kind are the conclusions of demonstrations. To these truths the intellect cannot refuse its assent, after having perceived their link with first principles and not before. [In I Perih., lect 14, n. 24]

As for the other truths that do not flow from first principles and cannot be proved by a necessary connection with the truth of these principles, the intellect remains free to assent or dissent.

But some apprehended truths do not convince the intellect to such an extent as not to leave it free to assent or to dissent, or at least to suspend its assent or dissent because of some cause or other; and in such cases, assent or dissent is in our power, and is subject to our command. [S.Th., I-II, 17, 6]

In this teaching on the object of assent we re-encounter the law of the perfection of human knowledge, whose actualization is the function of judgment. The intellect’s perfection is the conscious grasp of being and all its riches. But, just as apprehension enriches us with a segmented, disassembled world that is judgment’s function to reconstruct in us by means of composition, so does direct judgment give us a unified and therefore true world, but a world whose truth is observed as a fact rather than perceived in its nature and stability. That is why the intellect must again analyze the truth with which its knowledge is endowed in order to discover its value and establish a certain hierarchy among the immanent riches it possesses. This is the role of the act of assent; and it is not surprising that this perfective act of human knowledge should have a critical sense sufficiently strong to discern, among the truths it has capitalized, which ones are characterized by an absolute necessity securing them from every possibility of change and thus permitting the human mind to count on an investment so safe that no revolution or depression of the market of human truths will ever affect the value of the stock it holds. In the philosophical world the gold standard of infallible truth has never been abandoned, and, what is more, this gold standard has been identified with the primary truths measuring all truths whose stability merits the full confidence of the human mind. The role of the act of assent is therefore to register the intellect’s approval of the truths presented to it, absolute or relative approval depending upon whether the truth in question is presented to it with guarantees of infallibility or with possibilities of bankruptcy. Also, the function of dissent is to reveal the intellect’s disapproval in face of error, absolute or relative disapproval depending upon whether the error is presented as identical with the absurd or may possibly be changed into truth by means of modifications in the real that measures it.

This theory of assent, in relation to its proper object, formal truth, is explicitly, albeit concisely, stated in some rare texts of Aquinas. We shall quote the one that seems to us most strongly worded and shall briefly explain the passages whose conciseness might make them obscure.

The possible intellect, however, so far as its own nature is concerned, is in potency to all intelligible forms... Therefore, it has no intrinsic determination which necessitates joining rather than dividing concepts, or the converse. Now, everything which is indetermined with reference to two things is not limited to one of them unless by something which moves it. But only two things move the possible intellect: its proper object which is an intelligible form, that is a quiddity and the will, which moves all the other powers. [De veritate, 14, 1]

In this passage St. Thomas poses the problem of assent in relation to the mental act that gives the mind its object, i.e., affirmation or negation in whose term, the proposition, truth exists. But when it comes to adhering or not adhering to yes or no, our possible intellect, considered in itself, is indifferent, which is to say that it could adhere or not adhere just as well to affirmation as to negation, just as it can receive all material quiddities without preferring any one of them. Therefore, we shall have to explain what happens when our intellect loses its neutrality toward yes or no and accepts or rejects one of the two propositions, whether affirmative or negative. This fact can have only one explanation—the intervention of an agent, which for the intellect could only be its proper object or the will, whose efficacity would determine the intellect’s natural indifference and make it side for yes against no, or, vice versa, would make it assent or dissent. That is the way St. Thomas poses the problem of the act of assent in the foregoing text. Now we shall see how he applies this theory to the different mental acts, to determine which are acts of assent and which are not.

In this way, then, our possible intellect is related to the extremes of a contradictory proposition differently. For, sometimes, it does not tend toward one rather than the other, either because of lack of evidence, as happens in those problems about which we have no reasons for either side, or because of an apparent equality of the proofs for both sides. This is the state of one in doubt, who wavers between the two members of a contradictory proposition. Sometimes, however, the understanding tends more to one side than the other; still that which causes the inclination does not move the understanding enough to determine it fully to one of the members. Under this influence, it accepts one member but always has doubts about the other. This is the state of one holding an opinion, who accepts one member of the contradictory proposition with some fear that the other is true. [Ibid.]

Two cases are presented in this text. In the first the agent defaults, i.e., the truth is not evident in either affirmation or negation, and since the mind has no object to adhere to, it cannot side with either one of the alternatives: it makes an act of doubt, which is precisely the negation of the act of assent and of its contrary. The second case is more complicated: truth does appear to the mind in one of the two alternative contradictories, but this truth does not have all the intrinsic guarantees it should possess. There is factual evidence to show that the predicate is concretely and practically linked to the given subject, but we do not know the nature of this bond: Is it necessary or contingent? We do not know. Could this unity of subject and predicate be only accidental and therefore cease to be? Possibly. Thus, the mind opines for the truth as for a fact, but without absolutely opposing the other alternative. The intellect takes no definite stand, so there is no strict assent, because there is no compelling object or truth.

Sometimes, again, the possible intellect is so determined that it adheres to one member without reservation. This happens sometimes because of the intelligible object and sometimes because of the will. Furthermore, the intelligible object sometimes acts immediately, sometimes mediately. It acts immediately when the truth of the proposition is unmistakably clear to the intellect from the intelligible objects themselves. This is the state of one who understands principles, which are known as soon as the terms are known... in this case the very nature of the terms immediately determines the intellect to propositions of this sort. The intelligible object acts mediately however, when the understanding, when it knows the definition of the terms, is determined to one member of the contradictory proposition in virtue of first principles. This is the state of one who has science. [Ibid.]

This text summarizes the causality of necessary truth upon our intellect, the grasping of which truth is comparable to the grasping of quiddities, because it is, in fact, the result of comparing two quiddative notions that imply each other either immediately in the case of natural principles, or mediately in demonstrative conclusions. The text goes on to describe the special case of the assent of supernatural faith, which enters into theological epistemology but not into the philosophical epistemology that concerns us here. Therefore, we shall proceed immediately to the conclusions St. Thomas draws from this analysis of the motor object of our act of assent, that is, of evident and necessary truth insofar as it draws our intellect out of its neutrality with respect to the affirmation and negation making up the two parts of the contradiction.

It is clear from what has just been said that assent is not to be found in that operation of the understanding by which it forms the simple quiddities of things, for there is no truth or falsity there. For we are not said to assent to anything unless we hold it as true.

Likewise, one who doubts does not have assent because he does not hold to one side rather than the other. Thus also, one who has opinion does not give assent, because his acceptance of the one side is not firm. The Latin word sententia (judgment), as Isaac and Avicenna say, is a clear or very certain comprehension of one member of a contradictory proposition. And to assent is derived from sententia.

Now, one who understands gives assent, because he holds with great certainty to one member of a contradictory proposition. Such one, however, does not employ discursive thought, because he fixes one side without any process of comparison.

One who has scientific knowledge, however, does use discursive thought and gives assent, but the discursus causes the assent, and the assent puts an end to it. For by the very act of relating the principles to the conclusions, he assents to the conclusion by reducing them to the principles; there the movement of the one who is thinking is halted and brought to rest. For in scientific knowledge the movement of reason begins from the understanding of the principles and ends there after it has gone through the process of reduction. [Ibid.]

In the order of pure knowledge, we may therefore include that, in abstracting from the specifying dynamism of the will—whose intervention is necessary in cases where intelligible factors are lacking—the only motor whose efficacy can infallibly produce intellectual assent-can determine the intellect absolutely to one of the members of the contradiction is immediately evident per se truth. Therefore, these are the first truths we analyzed and the sensible evidence that is immediately reducible to these first self-evident principles.

B. The act of assent

That the act of assent belongs to the second operation of the mind, nothing could be more certain, and all the texts are categorical on this subject: “In its activity of judging, the intellect has two acts: affirmation by which it adheres to the true, and negation by which it rejects adherence to error.” But can it be identified with every judgment in such a way as to be a constitutive factor of the second operation of the mind in its most formal aspect? This question has long been discussed, and there is no unanimity about its answer; however, its solution seems relatively easy as soon as the proper object of assent is determined. We have stated that this object is the formal truth of our propositions and thus a reality which cannot exist without a previous judgment; in this context, assent obviously cannot be identified with judgment or be one of its constitutive elements, since the object of assent follows upon the existence of a direct judgment of things. However, we are not going to support our position here by an analysis of texts, because that would be a very lengthy and useless procedure. But this is how we can prove that assent must have formal truth as its object and, consequently, that it cannot be identified with the nature of judgment itself.

Let us suppose that the ontological truth of the act of apprehension is the object of the act of assent, as a result of the intellect’s reflection upon its likeness and the thing measuring it, which is the way an act of judgment does take place. If this is the case, then assent is identical with judgment and to say that man is white and to adhere to the truth of this judgment is one and the same thing. However, if the ontological truth of the act of apprehension is the object of assent, the ontological falsity of this same act should be the object of the act of dissent, since the latter is concerned with the contrary of the object of assent. But, in Thomism, ontological falsity is meaningless: the intellect either apprehends the quiddity of things or does not, but it cannot err about the nature of things. If the object of assent is the ontological truth of the concept of apprehension, then dissent has no object. Besides, there is a teaching essential to Thomism that makes it forever unacceptable to Cartesianism, and that is the division of truth into the necessary and the contingent. If the truth that is the object of assent is the truth existing in the concept of the mind’s first operation, this truth can only be necessary, since the intellect is infallible in this first operation. Where, then, do contingent truths come from? And if there are contingent truths, they cannot be the object of assent, for the latter deals only with necessary truths, just as dissent deals only with necessary error. But if every judgment implies assent as an essential constituent, judgments about contingent things are impossible, and by that fact the whole field of opinion and dialectics is thrown out of the Thomistic synthesis. It is an undeniable fact that in Thomism opinion is a judgment, that contingent truth exists and is the daily and customary food of the great majority of men, and that this truth, which can exist only by and in a judgment, does not deserve the intellect’s assent; not only does it not deserve it, but to bestow assent upon contingent truth is to sin against the very nature of our intellectual power. Therefore, it is not possible to say that ontological truth is the motor object of assent, and, consequently, it is impossible to identify it with judgment properly so called, or to make it an essential element of its psychological structure.

Although, as we have just seen, assent is not identical with judgment, that does not prevent it from being a judgment; but what kind of judgment is it? In studying judgment as an act perfecting human knowledge, we saw that its function is to synthesize the concepts which the abstraction of the agent intellect provides to the possible intellect, and that this synthetic act must be measured by the unity of the real, which is the definition of truth itself. The existence of this judicative act is perceived in and by the act of judgment itself—which implies reflection upon the genesis of our concepts. But just as knowing a thing’s existence is not the same as perceiving its nature, so awareness of the existence of truth is not identical with awareness of its nature. There must be a second act of reflection whose object is the truth or falsity of our affirmation and negation; it must perceive their quod quid est, i.e., the value of this truth possessed by our propositions. If this value is such that it can never be shaken or obscured, then the intellect, whose end or good is knowledge of the kind of truths whose values are eternal, cannot resist it; it surrenders and submits to the object of its love, and this is the definition of the act of assent itself.

But how can we judge the truth of our propositions? By analyzing the bond uniting predicate to subject. This bond can be of four kinds: either it signifies what the subject is, or what inheres in the subject by itself and absolutely as flowing from its nature, or what inheres in the subject with relation to another, or finally what is extrinsic to the subject. Now, a judgment concerned with the bond uniting or dividing subject and predicate is a modal judgment whose immediate object is the necessity or impossibility of the truth of this or that proposition, or the contingency or probability of the truth and falsity of our propositions. If the matter of modal judgment is necessary or impossible, it formally constitutes what St. Thomas calls assent or dissent; if its matter is contingent and possible, it constitutes what he sometimes calls probable assent or the judgment of opinion or of dialectic.

Although this statement may at first glance seem strange and foreign to the philosophy and vocabulary of St. Thomas, reflection shows its expression and doctrine to be in perfect conformity with the Master’s texts. For, as we have just seen, St. Thomas always relates assent to the contradictory opposition existing between affirmation and negation. For him, assent consists in adherence to one member of the contradiction and complete denial of the other alternative. Now, careful examination of the way assent to the truth of the principle of contradiction is stated shows this assent to be nothing but a modal judgment: it is impossible that the same thing both be and not be; it is necessary that every subject whatsoever be either affirmed or denied; it is impossible that contradictories be simultaneously true.

Here then is the exact situation of our problem. The first of all assents is stated as a modal proposition; on the other hand, all other immediate assents imply this first assent, and mediate assents can exist only insofar as they can be reduced to the principle of non-contradiction, for science and opinion are differentiated by the fact that the object of the former is reducible to this principle, whereas the object of the latter is not.

Science is incompatible with opinion about the same object absolutely, for the reason that science demands that its object should be deemed impossible to be otherwise; whereas it is essential to opinion that its object should be deemed possible to be otherwise. [S.Th. II-II, 1, 5, ad 4]

Therefore, since assent bears upon the only immediate and necessary evident truth and, by its intermediation, upon necessary truths whose absolute evidence depends on their reduction to the evidence of first principles, and ultimately to the evidence of the principle of non-contradiction, since, on the other hand, the assent of contradiction is nothing but a modal judgment stated in a modal formula—we may legitimately conclude that assent, in the strict sense, is a modal judgment concerned with the nature of the formal truth of a direct judgment whose term is the being of things. It is a judgment of judgment, therefore, it is not identical with the nature of every judgment, nor can it be considered as an essential element in every second mental operation. In fact, it designates nothing other than that group of propositions which are characterized by their adequation with the real and by perception of the bond of perseity unifying predicate to subject. This is a bond that cannot be other than it is, which is what constitutes the necessity and infallibility of truth. Such is the nature of the act of assent and its object.

Section II: Assent and Certitude

It may perhaps seem surprising that through these many pages devoted to studying the knowledge of truth, the problem of certitude has not been mentioned, whereas this problem appears to have preoccupied all thinkers from the Greek skeptics to our day. It is even more surprising that an examination of the legion of texts in St. Thomas about the problem of knowledge, both natural and supernatural, reveals none whose sole object is the study of certitude. Certitude is always mentioned as being part of perfect knowledge, but its function in epistemology and its constitutive elements are never studied in themselves. “Happiness consists in a perfect operation. Now perfect knowledge requires certitude, and that is why we cannot be said to know unless we know what cannot be otherwise.” Perfect knowledge gives to the intellect its natural good, truth, and perfect possession of this truth; therefore, it implies assent or modal judgment upon the value of the truths we possess. That is why St. Thomas, in the text quoted above, describes perfect knowledge or certitude in terms of assent or modal judgment—we cannot be said to know unless what we know cannot be otherwise—which is the definition of the object of assent, infallible truth. Certitude and assent should therefore be identical, which would imply that where there is no assent, there can be no certitude. However, this identity seems difficult to affirm, as the following text proves:

Whoever considers an element belonging to several things as belonging properly to one of them, is necessarily on the way to error. Now certitude of adherence does not belong properly to the act of faith; first because it also belongs to the intellectual virtues of science, wisdom and understanding; then because it is common to both true and false faith... for men do not adhere any the less firmly to truth than to falsity: finally because certitude of adherence does not always result from a habitus but may also result from the free willing of someone who can firmly establish his assent to truth and to falsity bef ore possessing a habitus of truth. [Quodlibeta, 6, 6]

Thus, were it true that assent is always accompanied by certitude, it would be impossible to make certitude a property of assent, since certitude can accompany error. In order exactly to know what relations exist between assent and certitude, we must give more precision to the meaning or meanings of this word, as it is used in St. Thomas, and establish some kind of order among the different meanings it can have. That is what we must do first; then we shall try to discover the exact meaning of certitude when it necessarily accompanies the act of assent.

A. The meanings of “certitude”

The word certitudo is taken from the Latin word cernere, which is itself drawn from the Greek krinein. Now, the root of this word, krei, expresses the idea of separation, distinction, which has given to its Latin. and Greek derivatives the following meanings: to sort, to distinguish, to decide, to see clearly, to be fixed. Its philosophical meaning has been largely the work of Aristotle and his Greek and Arabian commentators, whose translated works became the heritage of Latin Scholasticism. It was in these texts that St. Thomas found the philosophical meaning of certitude that he used constantly in his works, either keeping its first Aristotelian meaning or the meaning the Arabian thinkers had added to it, or giving it new meanings to meet the needs of the new problems brought up by revelation.

St. Thomas kept Aristotle’s ontological meaning of certitude, by which it expresses the precise dimensions of the order of quantity. He also kept the methodological function of certitude in the hierarchy of the sciences arranged according to their necessity. The ontological sense of Aristotelian certitude had primacy over all the other meanings; it was its formal meaning. But in St. Thomas there was a transposition of the Aristotelian meanings and a union of the subjective determination of knowledge with the ontological determination of its object. In the Thomistic context the first and formal sense of the word certitude belongs to the epistemological order, whereas its derived meanings belong to the order of the object and appetite.

Certitude exists in two ways in a thing: by essence and by participation. It exists by essence in the cognitive power and by participation in everything which is infallibly moved towards its end by the cognitive power; which explains why we say that nature operates with certitude inasmuch as the Divine Intellect moves every being towards its end with certitude. [S.Th., II-II, 18, 4]

The cause of this formal or essential certitude, whose subject is the knowing power, is more efficient the more it determines the intellect to unity:

Certitude is nothing but the determination of the intellect to unity. The degrees of certitude depend therefore upon the degree of power possessed by the determining principle. The intellect’s determination to unity is accomplished in three ways, as we have said. In the understanding of principles the determination is caused by the fact that the light of the agent intellect renders the object sufficiently evident in itself. In knowledge of conclusions the determination to unity is caused by the fact that the rational conclusion is reduced to the intrinsic evidence of the principles. In faith, by the fact that the will commands the intellect. [In III Sent., 26, 2, 4, sol. 3]

This text gives us both the definition and the division of certitude, but it is quite curious to observe that the definition and division of certitude are identical with the definition and division of assent, as given us. It does not seem possible to reconcile this identification with the group of texts describing certitude and situating it in a very different context from that characterizing the judgment of infallible truth which is assent. We shall try to solve this problem by showing that, in a certain sense, certitude and assent always go together for they are essentially complementary, and that, on the other hand, both assent and certitude can be used by St. Thomas in wider meanings and contexts which are still legitimate but whose precision and technical character have lost all their primary value in order to take on another that corresponds better with our usual way of talking.

B. The correlative character of assent and certitude

To understand the apparent identification established by Thomistic texts between the notions of assent and certitude, we must recall an essential aspect of Thomistic epistemology: the problem of knowledge must be situated in a context of imitation of divine perfection, and the problem of the knowledge of truth must also be understood as an essentially perfective factor of apprehension. But, just as the knowledge that consists in the apprehension of quiddities obeyed an evolutionary process wherein confused and indistinct vision of the real was gradually replaced by a distinct and precise grasp of it, so in the second operation of the mind there is movement from the imperfect to the perfect in awareness of truth, which we first know as existing when we are in the act of judging the real, and then know in its deep nature and indefectible value in the reflex and modal judgment that is assent. Now, there is a natural law by which beings tending toward their end or perfection perform a series of acts that bring them closer and closer to their good, until a last act takes final possession of their end, and then they rest in this possession because they have attained the term for which they are made. Movement toward possession, possession of the true end, and rest or joy in the good possessed—these are the three aspects of the natural dynamism of all beings that have not but must attain their perfection. But this is precisely the case with man as intelligent: made to know all things, he is born ignorant; made to know reality as it is, he is compelled by his natural process of abstraction to fragment the real in order that it may enter into him, even though he must reconstruct its unity by judicative activity; made to be perfectly aware of the immanent reconstruction of the exterior world, which constitutes the domain of truth, this awareness occurs and illumines the intellect only gradually. Analysis of assent has shown us the human intellect exercising a natural, spontaneous, necessary act that takes possession of a natural good for which it is made, namely, infallible truth. To reflection, certitude appears as the repose in the possession of this good, a sort of partial beatitude of the intellect caused by the presence of truths, of which nothing in the world could ever deprive it.

It may seem strange in Thomistic philosophy to present the doctrine of certitude in a context of appetite, and to bring the analogy of love and delight or repose into play in the order of knowledge! And yet, nothing could agree more with the doctrine and texts of Aquinas, as soon as we see that the object of assent is formal truth and that the object of certitude is this same truth considered as its place of repose. For formal truth is immanent to our intellectual faculty and is formally the proper good of our knowing power, inasmuch as it is a natural thing.

Everything that comes from God receives from Him a certain nature by which it is related to its final end. But it is also true that every power has a natural appetite... with respect to its proper good... and with the exception of the will all the powers of the soul are necessitated by their objects. [In III Sent., 27, 1, 2]

Our cognitive power therefore has a natural, necessary, and unconscious tendency toward truth, a sort of natural love that is the basis of all our acts of knowing, and it sets off a whole series of inquiries among which some cannot attain truth.

Several philosophers have let themselves be guided by truth so far as to affirm that the principles of things are contraries; which is indeed true, but they have not been impelled to this statement by a proof so much as they have been compelled to it by truth itself. For truth is the intellect’s good and the term of its natural ordination; and just as things without knowledge are moved toward their end without knowing it, so sometimes does the human intellect by a natural inclination tend toward truth although it does not perceive its nature. [In I Phys., lect 10, n. 5]

Thus, the intellect’s natural appetite for truth makes it discover the existence of some truths even when it does not know what truth is. This unawareness results from our ignorance and lack of reflection upon the intellectual riches we possess; this is the way we apprehend the truth of first principles—we assent to them by a sort of instinct for truth. But our intellect is light and luminosity, and of this we should be aware. It is reflection that makes us relive in the light what an invincible tendency of nature has produced. Now, this reflection upon natural assent and the nature of its object demands that we conceive it as a spontaneous or immediate, necessary, and infallible possession of the human intellect’s proper good, whose efficacity it cannot resist. This means that when the intellect meets the truth for which it is made, it grasps it; truth becomes consciously present to it. The intellect rejoices in this presence, rests in it, and this is certitude, or joy in the good possessed. “Delight which is nothing but repose of the natural appetite is found in every power upon its union with its object.” Now, this natural repose or delight of a power in the presence of its object, or end, has several aspects that throw light on the explanations given about the nature and variety of the act of assent and its certitude.

When the beloved is really present as much as it possibly can be, delight results as the effect of a perfectly harmonious unification; when the beloved is completely absent, the greatest sorrow reigns; finally when the beloved is partly present and partly absent, delight is mixed with sorrow. [In III Sent., 27, 1, 3, ad 3]

Let us apply this sketch of the relations between appetite and the presence of its good to the speculative data on assent and certitude considered as the possession of the intellect’s good and joy or repose in this good.

(1) In intellectual assent to the truth of first principles there is awareness of the presence of necessary truths in the soul, and a grasping of the nature of their necessity, thanks to the agent intellect that makes the contradictory opposition between yes and no visible to the possible intellect. This intellectual vision or possession makes the motor good of our cognitive power actually present as much as it can be. The result of this perfectly harmonious conjunction between our cognitive power and its good is joy or repose in the necessary truth possessed, and this is absolute intellectual certitude with no admixture of any incertitude, because this truth is totally present or perfectly evident.

(2) In scientific assent, possession or presence of the intellect’s good is brought about by means of analysis or resolution; therefore, reason or cogitatio is always in play, as long as the bond linking the concluded truth with the truth of first principles has not been established. Once this bond has been established, the intellect is fixed and rests. And this is the definition of scientific certitude which results from the intellect’s testifying to itself that that for which it is made is actually and permanently present.

(3) In the assent of faith, the intellect does not possess supernatural truth, because such truth is beyond our intellect’s illuminative capacities; therefore, the good is absent, and relations with it can only be established by the testimony of another, in this case, infallible divine truth. By means of this sort of presence by proxy, the intellect is made captive to the motion of the will; but since this captivity is not the effect of intrinsic evidence, the intellect is deeply dissatisfied and restless; certitude and joy depend on the will that, being in the presence of the absolute good, divine truth, adheres to it with all its strength.

This third kind of assent, accompanied by certitude that does not stem from joy in the intellect’s present good but from a voluntary determination, explains why in some texts St. Thomas speaks of assent and certitude that have bearing on contingent truth and even on error. In all these cases, assent and certitude do not result from the presence of infallible truth to the intellect but are the product of voluntary pressure commanding adherence either for practical reasons of activity, or through prejudice, ignorance, rashness, or lack of reflection, which may imply lack of prudence and therefore a moral defect. The assent and certitude produced by sensible evidence is in a class by itself, experimental certitude, which has value only for the duration of the sensation and in no way increases our treasury of stable and certain truths.

Thus, we may conclude that when certitude is taken formally as intellectual repose of our power in possession of its good (necessary and self-evident truth), it always accompanies assent taken in the sense of value judgment on truth. But when certitude is taken in a participated sense-depending on the human will as free and determined to goods that are not proper or present to the intellect—then certitude, as well as assent, in no way resembles the certitude and assent we have been discussing, for these depend objectively upon the speculative intellect only and the essential laws controlling its functioning. But the certitude depending on will leads us into the domain of human liberty with its capacity for good and evil; we leave the spontaneous and autonomous structures of the intellect to enter the realm wherein will can rule intellect when the latter is no longer necessitated by its infallible mover, necessary truth, which is self-evident in itself and for us.

Some truths which are apprehended do not convince the intellect to such an extent as not to leave it free to assent or to dissent, or at least suspend its assent or dissent because of some cause or other; in such cases, assent or dissent is in our power, and is subject to our command. [S.Th., I-II, 17, 6]

Such are the correlations existing between assent and certitude in the doctrine of St. Thomas, when these two words are taken to mean the natural activities of the intellect confronted by its proper good. Such also is the lack of correlation between these two words when used in a context of free will where choice exists because the intellect is not necessarily determined by the evidence and infallibility of truths, but by their value as the absolute good for man, taken as a whole or in one of his aspects. In this latter alternative, assent signifies conviction, and certitude means the practical satisfaction that the decision taken brings to action.

Conclusion on Value Judgment About the Truth of First Principles

With this chapter on assent, on the value judgment of the infallibility of natural human truth, we bring to a close our study of knowledge as a natural act rooted in sensibility, but gradually disengaging itself to evolve toward a purely spiritual possession of the universe in which we live. Spiritual and fragmentary in the act of apprehension, human knowledge is synthesized and perfected by judicative activity that enables it to reconstruct in the soul a substitute for the ontological unity of the things on which it is nourished. This new activity puts it into a measured-to-measure relationship with the exterior real, and from this new aspect the world of truth and error appears in the human soul.

Now, it behooves us to be aware of this world of truth and error and to possess the control instruments enabling us to know when and how truth, our health, and error, our disease, dwell in us. In this field, as in that of apprehension, we have natural instincts for truth, by which we apprehend its existence as soon as it appears in the very simple judgments called primary or immediate judgments, dealing with the most fundamental and evident notions of the human intellect. Once the existence of these truths is apprehended, we have to judge their validity, see their essential structure, and make judgments so as to arrange them in hierarchy and observe their quasi-eternal value. Here again we have a natural act, called assent, which is irresistibly attracted by the necessarily evident truth expressed by the first judgments. Once assent possesses this intellectual good, the intellect delights in it by and in the certitude that is nothing but our intellect’s repose and quietude in the unshakable security of the treasures it possesses. Such is the progressive advance of human knowledge and its evolution toward more and more immanent and therefore perfect knowledge of the exterior universe of which man is a part, and which he must use to live the life of the mind and to attain his destiny.

CHAPTER 12
INFALLIBLE KNOWLEDGE OF MEDIATE TRUTH

In the two preceding chapters we studied the birth of some infallible truths, our knowledge of these truths, and our value judgments about them. But examination of these first truths shows that their content is vague and that, in the realm of truth, it corresponds to the content of being as first known in our awareness of things. Just as our first confused grasp of being is but the starting point of a long inquiry that normally leads to being as being, so natural truths, grasped with absolute evidence and certitude by the intellectual habitus, are only the starting point for reason’s long and painful pursuit of more and clearer truths that will lead it to beatific truth itself, that is, to the total truth in which reason’s ultimate happiness lies.

Now it is not possible that man’s ultimate happiness consist in contemplation based on the understanding of first principles, for this is most imperfect as being most universal, containing potentially the knowledge of things. Moreover it is the beginning and not the end of human inquiry, and comes to us from nature and not through the pursuit of truth. Nor does it consist in contemplation based on the sciences that have the lowest things for their object... It follows then, that man’s ultimate happiness consists in wisdom, based on the consideration of divine things. [C.G., III, 37]

To this realm of truth which escapes primary evidence and assent belong all the truths called mediate. Their extent is as vast as the power of human reason itself.

Natural human knowledge can extend to those things which we can know under the guidance of natural reason. And there is a beginning and a term of the natural knowledge. It has its beginning in a kind of confused knowledge of all things, in so far as man naturally has within him a knowledge of the general principles in which, as in seeds, there virtually preexist all the objects of knowledge which can be known by natural reason. This knowledge reaches its term when the things which are virtually in the principles are expressed in act, as animal generation is said to reach its term when the animal, with all its members perfect and distinct, is developed from the seed of the animal in which all its members preexist virtually. [De veritate, 18, 4]

Therefore, mediate truth means everything that comes within the perspective of science and philosophy, insofar as these intellectual disciplines have as their term of inquiry truths whose evidence is not immediately grasped by the mind. Like all truth, this mediate truth belongs to the realm of cognitive life since it is one of its effects. It must therefore be studied according to the essential requirements of every vital activity, requirements arising, on the one hand, from immanence and, on the other, from specification by an exterior term. Furthermore, since mediate truth results from the difficult and delicate workings of a fallible reason, we must know the processes that ensure legitimacy and health to the gestation and birth of this new child of the mind. Finally, since by definition this truth has only borrowed evidence, it must be justified to the mind and must reassure the mind of its authenticity and value. From these three aspects of our problem result the three sections into which this chapter is divided:

1. The nature of the operation giving birth to mediate truth.
2. Method or art of discovering mediate truth: analysis and synthesis.
3. Value judgment on mediate truth: assent to conclusions.

Section I: The Nature of the Operation that Gives Birth to Mediate Truth

We have seen that judgment, the second operation of the mind, owes its existence to two sources. The first of these is our mind’s imperfection, the abstractive nature that forces it to “disassemble” the real in order to know it. The second source is knowledge’s own need for perfection, for knowledge seeks to grasp the real as it is, therefore, to grasp it in its unity, whence the need for an assembly line, which is none other than the second operation of the mind.

The third mental operation has its source in the same duality of principles, for it is, on the one hand. the result of the intellect’s imperfection and, on the other, the result of our knowledge’s need to grasp the real as one and integral.

As in the intellect, when reasoning, the conclusion is compared with the principle, so in the intellect composing and dividing, the predicate is compared with the subject. For if our intellect were to see at once the truth of the conclusion in the principle, it would never understand by discursion, and reasoning. In like manner, if the intellect in apprehending the quiddity of the subject were at once to have knowledge of all that can be attributed to, or removed from, the subject, it would never understand by composing and dividing, namely, that in the first apprehension of anything newly apprehended it cannot, at once, grasp all that is virtually contained in it. And this comes from the weakness of the intellectual light within us. [S.Th., I, 58, 4]

We reason and discourse because our intellect is imperfect, but also that it may become perfect.

The perfection of spiritual nature lies in the cognition of truth. But there are some higher spiritual substances which immediately in the beginning receive knowledge of truth without any movement or reasoning by a sudden or simple reception.... There are also lower spiritual substances which can arrive at perfect knowledge of truth only through a certain movement in which they go from one thing to another, in order to reach knowledge of things unknown through those which are known. This is proper to human souls. And this is why souls are called rational substances. [De veritate, 15, 1]

What we are looking for, then, is the nature of this cognitive activity that terminates in the discovery of truths not immediately evident and is characterized by its discursive aspect. In order to discover the essential aspects of any cognitive activity, we must first study it in its immanence, that is, in the very exercise of its activity and then in its specification, i.e., as measured by its exterior term or object. The study of these two aspects makes up the two, subdivisions of this first section.

A. Reasoning as an immanent activity

From its very beginning the study of this third mental operation shows us that if reasoning is characteristic of the human intellect’s very nature, it also reveals all the complexity of that intellect. In simple apprehension we were concerned only with showing how real things come into our mind and our vital reaction to the presence of these wealth-bearing guests. What we saw in judgment was a unification in which the mind takes the initiative in order to be measured by the real thing in the latter’s own unity. But in discourse or reasoning, what interests us is the ver diversity of the unifications produced by the judgment; we want to see what bonds unite them, to set up an immanent order within the multiplicity of our truths. The complexity of this operation is not surprising since it presupposes the actuation of all the previously studied elements by an activity that has neither the passivity of apprehension nor the spontaneity and natural infallibility of first judgments. We shall study this activity of reason first in its mode and then in its nature.

1. Discourse as a Mode of Rational Knowledge. The mode of the first operation of the mind is passive and abstractive; the mode of the second is concrete and compositive; the mode of the third mental operation is characterized by the discourse that is called reasoning. To discourse is to go from the knowledge of one truth to that of another, to proceed from the known to the unknown. It is a kind of movement in which reason tries to draw from the immediate and certain truths it possesses other truths which escape it.

Discursion expresses movement of a kind. Now all movement is from something before to something after. Hence discursive knowledge comes about according as from something previously known, one attains to the knowledge of what is afterwards known but which was previously unknown.

Precisely because of this typical mode of knowing, reason is distinguished from intellect, in the Thomistic vocabulary, not as a distinct faculty but as a complementary aspect of an intellect in whose shadow it works.

To understand is to grasp intelligible truth absolutely, and to reason is to advance from one thing understood to another, so as to know another intelligible truth... But man arrives at the knowledge of intelligible truth by advancing from one thing to another. And therefore he is called rational. Reasoning therefore is compared to understanding as movement to rest, or acquisition to possession. [S.Th., I, 79, 8]

Since discourse implies a kind of movement from one evident truth to another, the latter being linked in some way to the former, we must have a look at the two terms of this movement, for on the nature of these terms depends the mode of the knowledge properly called discourse. Comparison with the modes and operations of apprehension and judgment, which we have already studied, will clarify this statement. In the activity of apprehension we saw that the intellect could reflect on its concepts, divide and compare them, and arrive, at least ideally, at a definition. This division and comparison of concepts taken as absolute is not discourse but an orderly arranging of several concepts into a higher unity.

Also, in the judicative activity of composing and dividing concepts, comparison and division do not aim to discover a third concept possessing a higher unity, but aim rather to set up a sort of existential unity or multiplicity between concepts; here again there is no discourse properly so called. In order that discourse exist, this mental movement’s point of departure must be an already known evident truth that serves as starting point for the discovery of another previously unknown evident truth, whose coming into existence is not the result of chance but of its linkage to the evident truth which was the starting point. Thus, discourse always starts from either a categorical or hypothetical statement, to which it tries to link (or from which it tries to separate) one or more propositions in order to arrive at new evidence in which the discourse terminates.

This brief explanation has therefore shown that, as immanent activity, discourse cannot be an absolute starting point in the pursuit of truth, but that it always presupposes the existence of evidence already possessed and recognized as such. Still in this context of immanence, discourse has no value in itself; by nature it is destined to result in new vision and to disappear so that it may give way to vision. Essentially it is an intermediary between two judgments that it unifies or opposes, as the case may be. In the order of discovery and unification of mediate truths, it plays the role of composition and division in the conscious organization of our concepts, an organization that gives rise to immediate truth.

2. The Nature of this Third Operation. Whereas to know is to assimilate the real by being informed by it, whereas to know truth is to see that what we have become by knowing is conformed to that is real—to discourse is to seek. Since the act of seeking is naturally conditioned by the habits of the seekers and their preoccupations, that is, by what they are looking for, it is not surprising that this rational activity of the mind displays an extraordinary variety. This variety is revealed by the number of names Aquinas applied to this search, as well as by those added since the emancipation of modern science from the tyranny of philosophical methods of research. There is, first of all, the word cogitare, cogitatio, which means a sort of restlessness of mind in face of experienced ignorance, a restlessness that imposes on the mind an incessant activity until that ignorance is conquered. Inquirere, inquisitio, investigatio more typically indicate the search itself, the movement of reason which, haunted by curiosity, the desire to know or to act, seeks to discover the bonds that exist between what it sees and what still remains obscure, by using every indication and mark that might orient it in a definite direction. There are two other terms that express the gathering together of the diverse elements reason discovers in the course of its quest, as well as the comparison it sets up between them; these are collatio and conferre. There are also the words deducere and inducere, which more precisely indicate the manner in which the search is carried on and the nature of its starting point and destination; for induction takes a particular truth as the starting point of its search and terminates with universal evidence, whereas deduction or the syllogism proceeds in the opposite direction. Finally, there are two other words used by St. Thomas to describe the activity of reason; these are resolutio and compositio, which are opposed as methods of research. To these we shall return at length in the two remaining sections of this chapter.

Simply by analyzing the vocabulary, therefore, we can see that rational activity or discourse covers all the work man must do to arrive at truths that are not immediate. This activity is essentially labor, study. It includes everything that is the object of discovery and teaching and excludes none of the possibilities at the disposition of man to increase his knowledge and to unify it into a powerful synthesis. The whole field of inquiry—whatever its particular domain, be it philosophical, scientific, artistic—belongs to the nature of this activity, which is truly the Cinderella of the mind. To it is consigned everything that is laborious, long, and unsatisfying in the order of knowledge, both speculative and practical. If we limit our consideration to the exercise or immanence of this rational activity—without bothering about its specifying aspect, that is, the mediate truth toward which it tends by nature—we can easily see how extraordinarily supple it is. It is also clear that to confine this activity within the rigid framework of the demonstrative syllogism, or within the mathematical framework of Cartesian deduction, or, again, within the inexorable laws of scientific induction—to do this is to deprive it of a great part of its methods of inquiry and thereby to diminish our rational life as such. The whole domain of the probable, and that is the most extensive and daily aspect of human life, belongs properly to the reason and is its object. Whether or not we are aware of the procedure used, it is impossible to be a philosopher, a scientist, an artist, technician, moralist, or simply a man, without continually having recourse to this activity of linking, which is reasoning. Indeed, it is impossible for us to live humanly without trying to bring unity into the different kinds of knowledge we possess. Instrument of synthesis, reasoning or discourse as immanent activity is, therefore, essentially a principle of organization of the world of knowledge, insofar as this knowledge is directed toward truth of any kind. In the context of the immanence of intellectual life and of the progressive perfection acquired by this life as we become more aware and more autonomous, this discursive activity of our reason assumes its full meaning, for it belongs on the metaphysical plane that is typically assigned to epistemology by St. Thomas.

We have, indeed, seen that human knowledge takes on its full meaning in Thomism only in the context of the imitation of the divine, wherein man somehow breaks through his specific limitations to attain a sort of divine infinitude, by participating in God’s knowledge of things. In God, to know and to know perfectly are the same thing, whereas in man there is a distinction between his knowledge of things and the perfection of this knowledge, for there is a distinction between the being, of man and the perfection of his being, which is progressively acquired by means of accidents. From this results the explanation of the act of judgment as the perfecting of the being of knowledge that is apprehension; out of this also comes the conception of discourse as the complementary and perfective activity of the judgment. Just as substance is the source and end of the accidents perfecting it, so some accidents are the source and end of other accidents that perfect them. Now, that is exactly what goes on in the order of the knowledge of truth. Judgment, in taking possession of immediate truth is the source and end of reasoning, which renders distinct and actual the truths existing in a confused and virtual state in immediate truths.

Hence it is that human reasoning in the order of inquiry and discovery, proceeds from certain truths absolutely understood, namely the first principles; and again in the order of judgment returns, by analysis to first principles, in the light of which it examines what it has found. [S.Th., I, 79, 8]

The truth of first principles, despite its evidence and its certitude, is essentially vague and virtual, therefore imperfect, for it is but initial truth reflecting the indistinction and universality in the elements of simple apprehension of which it is composed. It is modest truth precisely because it reflects the imperfection of our intellect. And that is why, although reasoning has its source in the truth of these first principles, it is essentially the perfective instrument of such truth. For, thanks to reasoning, this first indetermination progressively disappears to be replaced by distinct vision enriched by the real, known no longer in its superficial appearances but in its nature and its existential opulence. This, in turn, brings us to the second aspect of discursive activity, that of its specification by exterior reality.

B. Reasoning as specified by an exterior term

In studying this aspect of discursive activity, we no longer concentrate on the inner process of inquiry and the laws ruling it, but rather on the exterior object that measures it and is its end. What is this object? What do we know when we discover mediate truth? In the study of human knowledge as such, i.e., apprehension of the real, that which specifies sensory knowledge is external accidents, whereas the specifier of intellection is being as grasped first in its moving actuality, then in its quiddity, and finally in its existing as such. In analyzing knowledge of immediate truth, we find it is concrete unity of the real thing in its accidental, substantial, and existential aspects that terminates the judicative act of composition; this is what St. Thomas called ipsum esse rei.

Besides substance, accidents, and the act of existing, can there be anything else in the real thing which is a genuine aspect of being and serves as term or object of discursive activity? There is the whole field of real relations that exist between real things, relations of cause and effect, of concomitance and succession, of law and fact, of harmony between parts of a whole, between means and end, finally of everything which, added to the absolute unity of the real, involves the thing in a plurality of relations or orders. This is the precise aspect of the real in which discursive knowledge should terminate.

1. Order Between Beings as Exterior Term of Reasoning. Order is a substitute for identity and is the soul of multiplicity. “In creatures, however, one form does not exist in several except by unity of order as the form of an ordered multitude... For we say that many men are a college, or an army, or a people.” A sort of composition or synthesis exists between different things whose distinction does not preclude every bond of kinship or origin. And wherever there exists a principle capable of unifying a multitude from within, whatever the nature of this principle and the realities it groups together, there is order. “Order always has reference to some principle. Therefore, since there are many kinds of principles... so there are many kinds of order.”

The ancients, in fact, discovered three categories of principles, of which the first unifies the multiplicity of local movements, the second unifies the becoming of things from within, and the third unifies this same becoming from without. The latter categories include the four causes, which are unifying principles in the respective domains of matter, form, efficiency, and finality. Furthermore, considered in relation to their effects, or to the diversity they unify, these four causes give rise to twelve different ways of being first principles, i.e., of being the unifying form of a multitude. If to these twelve modes we add the principle that measures and orders the multiplicity of local movements, we have thirteen possible bonds between beings, thirteen different orders that unify the different aspects of reality, consequently becoming the term of this immanent inquiry called reasoning or discursive activity. Actually, the real does not consist in a complex of properties and appearances, scattered at random, but in certain bonds, in certain constant relationships. It is the constancy and necessity of these bonds that are the object of our reasonings, in whatever field they may be discerned. And that is why the fact of necessity is intimately bound to the notion of principle and cause and is consequently part of order, which we have said is the specifying object of rational discourse.

Since there are as many different orders as there are unifying principles, and since, on the other hand, these diverse unifying principles are taken from the different levels of the real known by the intellect, the typical character of discursive knowledge varies according to the nature of the multiplicity whose unity of order we are trying to grasp. Thus, it is obvious that the order discerned by the mathematician in, the multitude of his equations is completely different from that discovered by the physicist in the phenomena of matter-energy; and the latter order is also totally different from that perceived by the sociologist reasoning on the social behavior of human beings. The scientific law expressing the coherence and constancy of phenomena in these different fields evidently corresponds to an objective order observed and analyzed by reason, but this order has not the same nature in the case of the mathematician, the physicist, and the sociologist, because the unifying principle around which the aspects of a frequently bewildering multiplicity and diversity are grouped does not have the same nature. And this unifying principle is often harder to perceive in human facts than in matter, as Lévy-Bruhl penetratingly remarks:

It is not facts that sociologists lack. In many cases they know enough of them to try to determine laws. What they frequently lack is the scientific apprehension of facts... the perception of the planes of cleavage which would make these laws apparent. [La morale et la sciences des moeurs, 1927]

These planes of cleavage are nothing but the organizing principle for sociological or other facts, a principle that transforms the multitude of facts into a whole obeying strict laws capable of explaining events and foreseeing them.

Now, after analyzing the nature of knowledge, we have to admit that not only do facts penetrate the human intellect, but also that natures, beings with their substantial and accidental, essential and existential aspects, come to lodge in this dwelling of infinite capacity that is our soul, and that if scientific facts, in the modern sense of the word, can dwell there, so too can the deeper levels of reality which are the objects of philosophical knowledge. Just as the scientist can, by his discursive activity, discover bonds, relationships between facts grouped around a hypothetical principle that sets order among them, so is it possible for the philosopher to discover, by means of the same discursive activity, bonds of coherence between the different aspects that reality offers to his reflection. And since the material dealt with by philosophical reflection is not uniquely phenomenal and factual, since it is not necessarily screened by an instrumentation which lets through only that part of reality capable of being numbered, and since this material comprises, on the contrary, each and every aspect of the real—the aspects observed by science as well as those perceived by the senses and intellect—the principles of order are much more varied in the field of philosophy than they are in science. Consequently, the links perceived by philosophic discourse are not based only on statistical laws but are formulated and stated in terms of cause and effect, necessity and contingence, in the philosophical meaning of these words. A causal order, such is the term or object of reasoning of philosophical knowledge.

2. Causal Order as the Term of Philosophical Reasoning. We must now elaborate a bit upon the nature of the causal order, which we have said is the object term of discursive activity in philosophy. To do this we will have to look back at some of the explanations already given during our analyses of the nature of human knowledge and of the knowledge of truth. We should not forget that, unlike the work of Descartes and Kant, our treatise on epistemology does not begin the study of human knowledge by identifying the latter with knowledge of infallible truth. The study of mediate infallible truth, in which we are engaged, comes at the end of an epistemological treatise because it is the effect of the nature of truth, which is itself the effect of the nature of human knowledge as such.

Now we have seen that, by nature, intellectual knowledge evolves progressively toward grasping the real as being by starting from the apprehension of the real as moving, and by proceeding successively to the intuition of its nature and to that of the perfective complexity which is the composition of substance and its accidents. In analyzing judgment and its exterior term, the ipsum esse rei, we rediscovered the same links that, within a being, unite the substantial and accidental, the essential and existential aspects. Finally, in analyzing those truths called primary and immediate, we saw that the perception of a causal link is natural to the human intellect as soon as it is confronted with contingent activity and an act of existing. Therefore, we have all the elements necessary for understanding the nature of the causal order that is the object term of discursive activity in the service of philosophical reflection and whose proper function is to measure mediate truth, just as the ipsum esse rei serves as the measure of immediate truth.

(a) Causal order in a being. To know is interiorly to live the exterior real, and this exterior real is first and foremost the whole material universe in which we live and of which we are a part. In order for us to be this exterior real, it must come into us, and this comes about by means of sensory knowledge, our only contact with the exterior world. But this contact is fragmentary and superficial; each sense reports only the exterior appearances of things; the intellect uses these appearances as so many routes to the inner depth, of the real, that is, to the comprehension of its nature. From this nature grasped in its distinction from accidents, grasped as substance with respect to its accidents, the intellect passes to unified knowledge of this substance and its accidents; this is the function of judgment, which knows accidents as inherent in substance. But beyond this factual inherence, the intellect wants to perceive the causal links that explain the why of this inherence, and this is the object of reason and the term of its discursive activity.

Judicative knowledge gives rise to a whole list of why’s in the soul. Why does the substance of things have extension? Why are things discontinuous? Why is there local motion and why all the qualitative and quantitative alterations that we observe in the real? Why are material beings measured by time and space? Why do they have distinctive qualities? Why do some beings have certain real relations, while others do not? Why are some beings active—and others passive? Insofar as reason can grasp the causal links binding these substances to these different accidents, insofar as these accidents depend directly or indirectly on substances as matter and form, as the source and end of everything issuing from it—to that same measure is the philosophical knowledge of these mediate truths possible. If these causal links cannot be perceived, then philosophical knowledge must give way to scientific knowledge in the modern sense of the word, be it physics, chemistry, biology, psychology, and/or their appendages, the historical and geographical sciences. [Régis here mistakenly separates philosophical from scientific knowledge of things through causes.] Since the constancy of the links discerned by these sciences depends upon observations of fact—on recurrences, on coexistences that are always factually interlinked, but not upon a genuine causal bond—the truth derived therefrom is probable and not certain in the philosophical meaning of this word.

(b) Causal order between beings. Modern science has accustomed us to a statistical order that acts like a sort of exemplary cause to which individuals submit, not as a particular being, but as helping to constitute a number within a multitude. The individual as such has no meaning or interest in an order of this kind for the very simple reason that science can exist only by virtue of a great number, and not through natures, for although nature exists in physical science, natures do not exist there. In the happy phrase of F.H. Bradley, the private nature of natures—of this whole world of substances and secondary qualities—is only a fiction; science has a hell from which it returns to interpret the world, but the inhabitants of that hell are only shadows. The philosopher does not consign the real to hell in order to explain it; that is, he does not convert it to shadows so that he may then number it and thus predict what will happen when he brings statistical laws into play. He is content to contemplate it in its existential and actual reality, as actually present to his mind. He does not try to impose an order upon the real for the purpose of subjugating it but tries rather to know an order that exists prior to his perception, serving as object for that perception and making it true. The hypothetical order, discerned by modern science in matter-energy, is part of this unified whole that is the physical world, but the philosopher discerns many others. [So does the scientist, if he is really scientific.] He is particularly interested in discerning the whole causal aspect found in living beings that take their nourishment from the physical world and thus use it on a different level. There is also all the reproduction of living things, this sort of vital reversibility that runs counter to entropy. There is the causality exerted by man upon the physical world, where he lives, and upon. other humans, his traveling companions. There is the causality of the astral world upon the organization of human life, upon the order of the seasons, upon the fertility and infertility of living things. And even though the philosopher cannot grasp the how of this causality, he can grasp its origin and its finality. Finally, there is the origin and end of this universe and of the beings composing it, as well as of the activities they initiate. In all that, the philosopher can perceive the principle and give a causal explanation. This brings us to the realm of metaphysics, a world into which the philosophy of nature introduces reason, in order that it may discover therein the why for the contingency of its existence and its activity, as well as the meaning of this act of existing and the activities flowing from it.

In that domain we perceive the principle of all things and, consequently, order in the best sense, the order to which all others are reduced more or less directly—because this Principle is God, and God is the beginning and end of all that was, is, and shall be.

Such, very briefly, is the causal order that we have offered as the object term of reasoning in philosophical knowledge as contrasted to [narrowly] scientific and mathematical knowledge. This order does not exist for science; it cannot be found by experimental methods; it is not instrumentally verifiable but has its own methods of research and its own verification. We shall now study its methods of research.

Section II: Method of Research Used by Mediate Truth

Every search for truth that is not immediately knowable has its own methods. Mathematics has its own, the experimental sciences have theirs; and it is the same with philosophical science and wisdom. What typifies the mediate truth discovered by the philosopher is its necessary and causal character. It must be seen in a causal order and in a necessary and proper causal order; otherwise, it is probable truth and depends not on philosophy but on dialectics, rhetoric, or poetry. Its method of research must therefore satisfy these requirements for necessity and causal properties, which means that the evidence serving as starting point for the perception of mediate philosophical truth must not only disclose the conclusion but reveal it to be a proper and necessary effect of the evidence that was the starting point. In order thoroughly to know the nature of the philosophical method of discovering mediate truth, we must, before analyzing the methods of discovery properly so called, seek out the nature of starting-point evidence. Hence, there are two subdivisions in this section: a) the nature of evidential principles, and b) the method of discovery that starts from such evidence.

A. The nature of the evidential principles of mediate truth

The proper context for the discovery of mediate or “concluded” truths is one of evident and infallible knowledge. The question involved here is: How can truths, whose evidence is not immediately visible to the intellect, be infallibly known by the intellect by means of a sort of participation in evidence and in the necessity of the immediate truths that we possess by a natural legacy that compels our intellectual consent? In order to participate in the evidence of these natural infallible truths, mediate truths must necessarily be caused in some way by this evidence. Since all participation implies causality, mediate truths must therefore be rooted in immediate truths.

Reasoning is compared to understanding as movement to rest, or acquisition to possession... And since movement always proceeds from something immovable... hence it is that human reasoning, in the order of discovery and inquiry, proceeds from certain truths absolutely understood, namely the first principles. [S.Th., I, 79, 1]

In the texts in which he explains the relations that must exist between evidential principles and the truths concluded therefrom, St. Thomas seems to maintain that mediate truth must spring from common principles or primary evidence, and, on the other hand, that it must necessarily proceed from proper principles, or lose its causal character. At first sight, it seems difficult to reconcile these two apparently opposed requirements; therefore, we shall have to examine more closely the nature of these common or first principles in their relationship with proper and immediate principles.

First of all, we must note that proper as well as common principles must be immediately evident and known in themselves, since, by nature, “concluded” truths must have an immediately evident principle as their starting point. But there are two kinds of immediately evident truths that are intuitively known by the human intellect.

For a thing to be immediately evident in itself, all that is needed is that the predicate pertain to the nature of the subject. For then the subject cannot be considered without it appearing that the predicate is contained in it. But for something to be immediately evident with reference to us we have to know the meaning of the subject in which the predicate is included. Hence it is that some things are immediately evident to everybody, as for instance, when propositions of this sort have subjects which are such that their meaning is evident to everybody, as every whole is greater than its parts. For everyone knows what a whole is and what a part is. Some things, however, are immediately evident only to those with trained minds, who know the meaning of the terms, whereas ordinary people do not know them. It is in this sense that Boethius says: There are two types of common notions. One is common to everybody; for example, if you take equal parts from things that are equal what is left of each of them is also equal. The other common notion is found only in the more educated; for example, that non-bodily things are not in a place.... For the thought of ordinary people is unable to go beyond imagination to reach the nature of incorporal things. [De veritate, 10, 12]

Of these two categories of evidence, one of which belongs to every man and the other only to the learned, the second can and must provide the necessary proximate principles for the discovery of mediate truth, since it contains the immediate cause of properties flowing from the nature of things. The first category could, at most, serve asa remote or first principle for a causal demonstration, with the exception of certain sapiential demonstrations in which universal evidence can be utilized by the philosopher in order to come to these conclusions. But we might ask ourselves this question: What bond is there between common principles and proper principles which justifies the statement that all sciences, in the philosophical sense of the word, are derived from first principles or from evidence that is indefectibly admitted by all? This is the bond that exists between a first principle and a proximate or second principle, and it belongs not so much to the order of efficient causality as to that of exemplar causality. For secondary principles share in the efficacy of first principles as the imperfect participates in the perfect, because all their intelligible value is derived from their measurement by primary evidence, especially by the principle that has priority over all others—the principle of non-contradiction.

In the first operation there is a first thing conceived by the intellect, namely, what I call being: and nothing can become intelligible in this operation except under the aspect of being. Furthermore, since the principle, “it is impossible to be and to not be at the same time,” depends upon the grasping of being as such, just as the principle, “the whole is greater than the part,” depends upon grasping the whole and the part, we must admit that the principle in question also is naturally first in the second operation of the intellect, that is, the operation which composes and divides. And no one can know by means of this second operation unless he has perceived this principle. For just as the whole and the parts can only be grasped if we have grasped being, so the principle, “the whole is greater than its parts,” can likewise only be grasped if we have perceived the above mentioned principle, which is the most certain of all principles.

The point of interest in the teaching set forth by the above text lies in the statement of the hierarchy of principles within universally recognized principles; for if it is by a sort of inclusion in the evidence of non-contradiction that all these evident principles are perceivable by the mind, it is with all the more reason that the proper principles of mediate philosophical truths contain this wholly primary evidence. This evidence will therefore be found at the origin of this discovery of mediate truth, but contracted, proportioned according to the anology or the mode of being it applies to, co-assumed, and applied within a more restricted vision of the real.

It is therefore true to say that the evidential principles which are the points of departure in the search for mediate truth are the first evidence infallibly accepted by the human mind, and that it is by and in the light of these infallible truths that reason succeeds in arriving at previously unknown truth. Thus, the infallibility of this new truth is but a participation in the infallibility of the evident principles with which the human intellect is naturally endowed. Since the object term of philosophical reasoning is the real order that exists between effects and causes, between its starting point and its goal, causal links must exist, the conclusion must spring from the premises that cause it and explain its content. Such must be the nature of the evidential principles of mediate truths in Thomistic epistemology.

B. The method of discovering mediate truths

Now that we know that the specifying term of philosophical reasoning is the causal order which links beings to each other and that its starting point is evidence which is immediate and necessary and which causes the truth conclusion, we must briefly examine the method the mind uses to make this ensemble of mediate truths (germinally contained in truth principles) pass from the virtual to the actual, without any, possibility of error, so that, at the end of its work, the intellect may possess an immanent universe perfectly arranged in a hierarchy modeled after the various causal relations concealed in the extraordinary diversity presented to the mind by the exterior world. What we must now study, therefore, is the problem of philosophical logic considered as the art of discovering non-evidential truth, quickly, easily, and without danger of error.

Now, everyone knows the profound contempt in which Descartes and modern thinkers hold Scholastic logic; to them, it is formal, vicious, and does violence to the mind without giving it evidence. And what is worse, it is absolutely sterile as an instrument for discovering truth. According to Descartes, the source of these capital sins of the Scholastic method is in its essentially synthetic character, which completely excludes analysis, by which fact the only method of discovering truth is excluded. These statements made by the putative father of philosophic method are owing to his total ignorance of the texts of ancient philosophers as well as to his identification of the method of discovery proper to mathematical truth with that of philosophical truth. In order to dispel these misunderstandings, and the unjust and gratuitous prejudices that contemporary minds have inherited from the father of modern epistemological method, we shall first of all establish the existence of a method of discovery by a brief historical excursion into the texts of Scholastic thinkers, then we shall see this method at work in the acquisition of the truths of science and wisdom.

1. The Existence of a Method of Discovery in Scholastic Texts. It is interesting to note in the philosophical texts of the ancients how extremely aware they were of the importance of method, as much in the field of discovering new truths as in that of a control for these new truths. They even have technical expressions to designate these two moments in the knowledge of truth. The method of discovery is called via inventionis, via inquisitionis, scientia inveniendi, whereas the method of control is called via seu scientia judicandi. These expressions, whose meaning is very general, cover two processes whose use is constantly and perfectly defined: analysis and synthesis. We shall take a brief lexicographical look at these two words in the vocabulary of Aquinas and his predecessors, in order to perceive their exact meaning. This will make it easier for us to understand their continual use as methodological instruments.

(a) The etymological meaning of analysis and synthesis. The words analysis and synthesis are obviously only modern transcriptions of the two Greek words analusis and sunthesis, which Latin writers translated by two typically Latin terms that have no verbal analogy with their Greek equivalents but nevertheless render their meaning perfectly. The Latin word solutio (alone or with a prefix, re-solutio), translates analusis, while compositio is a faithful rendering of sunthesis. We must center our study of Latin texts on the pair of terms, compositio-resolutio, in order to discover the philosophical meaning given by medieval thinkers to these terms, as well as the more or less extensive use they made of these two methodological processes in discovering new truths. Let us sound out the predecessors of St. Thomas so that we may be more familiar with the materials from which he drew to elaborate his philosophical method.

(b) What compositio-resolutio meant to St. Thomas’ predecessors. The correlated terms, analysis-synthesis, as defining the philosophical method of inquiry and discovery, are first found in a commentary of the Neo-Platonic Chalcidius on the Timaeus of Plato. Chalcidius explains this method in dealing with the already old problem of the number and nature of the principles of reality. Analysis consists in a movement of inquiry whose starting point is the least real, the least knowable, and is posterior in itself, but which is most knowable and prior for us, i.e., the sensible world. The terminal objective of this movement is the principle of material properties of this same sensible world, silva, or first matter. This notion of analysis corresponds to what the moderns call regressive deduction. Syntbesis, which follows analysis, makes use of the elements left aside by analysis, i.e., all the formal elements separated from matter. In using these elements, reason perceives that there is order among them and, since order implies harmony, that there is an intelligent principle of this order. Thus, it concludes upon the existence of a divine activity that organizes the world of change. In reading Chalcidius, we might get the impression of taking part in one of those long chains of thought” of which Descartes speaks, but with the difference that what Descartes calls analysis, Chalcidius calls synthesis, and vice versa.

The translations and commentaries of Boethius upon Aristotle are the second source from which medieval thought drew its doctrine on analysis and synthesis. In his translation of Aristotle’s work on logic, Boethius uses the word resolutoria as equivalent to analutika. Since analytics are the very method that philosophical knowledge uses in its own construction, he gives analytical process first place as an instrument for acquiring knowledge. To analytical process, which is judicativa veritatis, Boethius opposes dialectical or topical procedure, which is inventiva veritatis. It proceeds by way of composition or synthesis. These are the expressions and this the use of the analysis-synthesis terminology that entered into Scholastic logic and gave it its framework and vocabulary.

By his translations of pseudo-Dionysius, Scotus Erigena added further to the medieval explanation and usage of the method of analysis and synthesis. Erigena extended their field of application and made their usage more supple. Two points are to be noted in his explanations of them: first of all, contrary to Chalcidius, analysis is no longer restricted to the field of material principles of reality but can lead to the attainment of God; secondly, analysis and synthesis constitute not only an epistemological methodology but express the metaphysics of the real, as is shown by the title of Erigena’s major work, On the Division [i.e., analysis] of Nature.

Albert the Great, St. Thomas’ teacher, is probably Aquinas’ most important source, for in this contemporary’s works there is a very searching study of these two notions, a study in which are integrated statements of Chalcidius, Boethius, and Scotus Erigena. Albert the Great first uses the correlative terms analysis-synthesis to describe the intellectual act of apprehension. In this activity, synthesis consists in that knowledge of the singular through the universality of our concepts by which we grasp the formal elements of the thing; whereas analysis is the inverse process, consisting in the formation of the universal starting from the singular, a process whose result is a more-known quoad se and less-known quoad nos. He makes use of these two notions to explain the method of philosophical knowledge. He divides this method into two sections: a method of inquiry or discovery that he identifies with the Topics or dialectics, and a method or science of judging that he identifies with the Analytics. The first part of the latter method corresponds to the analysis of conclusions into their formal principles, whereas the second part seeks the ontological principles of these same conclusions.

What have we learned about analysis and synthesis, now that we have made this inquiry into the notions that the ancients held about them?

First of all, we know that these notions are as old as philosophical method itself, since they are an essential part of logic. Of these two, analysis is more important in the order of definition and reasoning because it provides an intuition of essences and of the mediate truths discovered by synthesis, whereas the latter plays a preponderant role in the discovery of new truths.

Furthermore, we know that the process of analysis goes from the complex to the simple, from what is less in being and less knowable in itself to what is greater in being and more intelligible, from the effect to the cause, from the divisible to the indivisible; whereas the process of synthesis proceeds inversely, going from the simple to the complex, from the one to the many, from cause to effect.

Finally, we know that although analysis precedes synthesis in the order of discovery of new truths, synthesis is prior in the order of explanation, i.e., not only as a teaching procedure but especially as a method of explaining the real and our knowledge of the real.

(c) Resolutio-compositio in St. Thomas. St. Thomas utilized all the discoveries made by his predecessors. But through his talent for using other discoveries to add new perspectives to Truths, perspectives whose only limits are those of the human intellect, he applied these notions to previously unforeseen fields. Here is a brief account of the different meanings these two words have according to their context.

Compositio and its equivalents: Composition or synthesis is union and not unity, and consequently it implies diversity. By virtue of its nature, synthesis has very diverse characteristics, depending on whether the parts to be united are homogeneous or heterogeneous. Thus, a heap of stones is unified by place, the materials in a house are unified by the idea of the architect, a mixture by its form, the elements of a number by the order existing between them. There is a synthesis of essence and existing, of matter and form, of substance and accidents, of parts in a whole. Synthesis enters into explanations not only in the field of the exterior real but also in epistemology; it is to be found in the formation of a definition, of judgment, and of reasoning.

Compositio is not the only word used to mean synthesis; we also find, in its place, inventio, inquisitio, collatio rationis, deducere, ordo, ordinare. This group of words, constantly used in the works of St. Thomas, shows the importance of synthesis as an essential factor in his philosophical method.

Resolutio and its equivalents: At times St. Thomas gives a metaphorical meaning to resolution, but most frequently he uses it in a very definite technical sense. It accounts for the decomposition of mixtures into their elements and of these elements into matter and form. It also describes the return of effects to causes, of means to the end, of particular notions to first notions, of judgments to simple apprehensions, of conclusions to principles. Like synthesis, analysis is thus adapted to the field of existing as well as to that of knowing. The word resolutio is not alone in expressing these notions; very often the following words are found in its stead: reductio, examen, abstractio, inducere, via judicii et divisio. This diversity of vocabulary makes a lexicographical study longer and more difficult, but at the same time it shows the functional scope which analysis has in the philosophical constitution of our knowing.

Thus, analysis and synthesis are two antinomic processes used by the mind to derive from the real the secret of its nature and of the order resulting from the different bonds that beings establish between each other. Never could analysis be transformed into synthesis, or vice versa, for they are irreducibly opposed procedures, one of which is always the opposite of the other. Now we shall study analysis and synthesis as philosophical processes by means of which our reason, using first truths as a sort of springboard, rises to the pursuit of new truths more distinct but less evident than the first, in order to get a concrete and unified grasp of being according to its mode of existing, thus giving rise to new adequations between our intellect and the real, and, therefore, to the discovery of hitherto unperceived truths. This will show us the dynamism of analysis and synthesis in this work of inquiry and discovery that reason sets up in order to bring a variety of nutritive and fortifying foods to the banquet of truth to which its nature issues an invitation with no possibility of refusal.

2. Analysis and Synthesis as Methods of Philosophical Knowledge. Philosophical knowledge has always been, and will always be, a knowledge of things through their causes, both intrinsic and extrinsic. Because these causes can be explanatory at a double depth of being-that of the accidents of real things taken as particular and diverse (accidents whose existence is habitually given us by the senses), and that of substances and of being, taken as such (grasped only by the intellect)—there is a double exploration of the real. The first is concerned with the immediate causes of phenomena perceived by the senses, or by their scientific extensions that are technical instruments. The second looks for remote or first causes that are primarily the constitutive elements from which each being results as such, and then their origin and unique end, i.e., their last principle in the order of efficiency and finality.

A truth which is known through another [i.e., a mediate truth] is understood by the intellect, not at once, but by means of the reason’s inquiry, is the term of this inquiry. This may happen in two ways: First, it so happens that it is the last in some particular genus; secondly, it so happens that it is the ultimate term of human knowledge. And since things that are knowable later in relation to us are knowable first in their nature, hence it is that which is last with respect to all man’s knowledge is that which is knowable first and chiefly in its nature. And about these truths is wisdom, which considers the highest causes...

But in regard to that which is last in this or that genus of knowable truths, it is science that perfects the intellect. [S.Th., I-II, 57, 2]

Therefore, philosophical knowledge is made up of two categories of mediate truths, and it is the task of analysis and synthesis to discover them. These truths are measured by being in the process of becoming as such, and their object is being as being. The truths of the first category belong to the field of the philosophy of nature, while the second truths belong to the realm of metaphysics or wisdom. Although the truths in these two fields differ in nature, the method used by reason to discover them is the same, since it is always a question of mediate truths to be perceived as the result of a rational effort of either analysis or synthesis. Consequently, in our study of this method we shall not be unduly concerned with the duality of its fields of operation. This duality affects the content of the discovered truths more than the way to discover them. For analysis as a process of discovery always starts from a truth that is more known to us and has as a term a truth more knowable in itself; whereas synthesis proceeds exactly to the contrary.

In every inquiry (inquisitio) one must begin from principle; and if this principle precedes both in knowledge and in being, the process is not by way of resolution, but rather by way of composition; for to proceed from cause to effect is to proceed in a composite way, since causes are more simple than effects. But if that which precedes in knowledge is later in the order of being, the process is one of resolution, as when our judgment deals with known effects, which we reduce to their simple causes. [S.Th., I-II, 14, 5]

Starting from this rather laconic description of analysis and synthesis, we shall try to get a view of their true nature as instruments for discovering new truths that proceed from evidence already possessed. To facilitate our understanding of these two activities of our reason, we shall deal with them separately, starting with analysis and then proceeding to synthesis.

(a) Analysis as a method of discovering mediate truth. For St. Thomas, as for all his predecessors, the analytic method of discovering truth is characterized by the fact that its point of departure is better known to the seeker but less knowable in itself. This distinction between what is more evident or known in relation to us, and what is more evident or perceptible in itself, is fundamental in St. Thomas. It is, in fact, bound up with the very nature of the procedure man uses to acquire knowledge, a process by which he enters into contact with sensibles before arriving at the intelligible. This is one of the characteristics of the rational method in the vocabulary of St. Thomas.

In a third way a method is called rational from the rational power, that is, inasmuch as in our procedure we follow the manner proper to the rational soul in knowing; and in this sense a rational method is proper to natural science.... First in this respect that just as the rational soul receives from sensible things which are more known relatively to us, knowledge of intelligible things which are more known in their nature, so natural science proceeds from what is more known relatively to us and less known in its own nature. [In lib. De Trin., 6, 1]

Discovery by means of analysis is therefore coextensive with demonstration quia or a posteriori, i.e., it enters into every argumentation that starts from a sign and an effect in order to get back to the existence of what is signified and of the cause when the sign and effect are more known relatively to us than is the signified and the cause, whose intelligibility is greater in itself. This is the normal situation for the great majority of truths belonging to the field of natural philosophy.

Secondly, natural science uses a rational method in this respect: that it is characteristic of reason to move from one thing to another; and this method is observed particularly in natural science, where we go from the knowledge of one thing to the knowledge of another, for example, from the knowledge of an effect to the knowledge of its cause. Nevertheless the procedure in natural science is not to go simply from one thing to that which is other according to reason and not other in reality, as when we go from the, concept of animal to the concept of man... But in the case of natural science in which demonstration takes place through extrinsic causes, something is proved of one thing through another thing entirely external to it... and on this account natural science among all the others is most in conformity with the human intellect. [Ibid.]

This method of finding truth does not enter into play merely in the philosophy of nature; on it depends that whole part of metaphysics or wisdom which, starting from contingent and created realities, rises to the existence of necessary causes and especially of the first cause of all things: God as the creator and end of the universe. Thus all the proofs of the existence of God, and of the existence of His attributes, belong to the realm of thought that is the analytic method, because they have as their starting point something better known to us, and as their goal that which is more knowable in itself but less known to us.

Some things are knowable to us through themselves; and in bringing such things to light the speculative sciences use their definitions to demonstrate their properties, as happens in the sciences which demonstrate propter quid. There are other things which are not knowable to us through themselves but through their effects. And if indeed the effect is adequate to the cause, we take the quiddity itself of the effect as our starting point to prove that the cause exists and to investigate its quiddity, from which in turn its properties are made evident. But if the effect is not adequate to the cause, then we take the effect only as the starting point to prove the existence of the cause and some of its conditions, although the quiddity of the cause is always unknown. And this is what happens in the case of the separate substances. [Ibid., 4]

This passage is capital for the understanding of the analytic method in philosophical science. Every time the human intellect cannot grasp the substance of things intuitively, or therefore the cause of their properties, it must proceed analytically, i.e., from the effects to their cause. Now this situation is natural to the human intellect, as soon as we admit its dependence on the senses; for being unable to grasp the substance of things intuitively, it has to pass through the intermediation of their accidents to their definition. This is what happens in the field of material natures whose accidents, being adequate to the substance that is their source and end, permit of a more or less precise grasp of the very essence of reality. But when it is a question of realities other than material substances, and particularly when it comes to the sole cause of everything that is, then no effect can bring us to perceive the essence of this cause, and the analytic method terminates in quia est, the simple fact that the cause exists.

Now we cannot know the quiddity of separate substances from what we receive from the sense, although by means of sensible things we can come to know of the existence of these substances and some of their conditions. So we cannot know what a separate substance is through any speculative science, although through them we can know of their existence and some of their conditions; for instance, that they are intellectual, incorruptible and the like. [Ibid.]

All natural theology or theodicy comes under the sign of analytic method, since it is concerned with the existence of God as efficient, exemplary, and final cause of all the created perfections whose nature our intellect can know, although it cannot use this knowledge to help it grasp the nature of Him who causes these perfections. This is what the Angelic Doctor calls sapientia de altissimis, ad altissima, as opposed to wisdom ex altissimis which starts from the understanding of things divine to explain creatures. The distinction between ratio superior and ratio inferior has the same meaning in his teaching, because it designates two distinct functions of human reason, one of which starts from the creator to explain creatures, whereas the other uses creatures in order to understand divine things.

Now these two, namely eternal and temporal, are related to our knowledge in this way, that one of them is the means of knowing the other. For in the order of discovery (via inventionis), we come through temporal things to the knowledge of things eternal.... But in the order of judgment (via judicii), from eternal things already known, we judge of temporal things, and according to the laws of eternal things we order temporal things. [S.Th., I, 79, 9]

All these demonstrations that deal with the eternal or divine as the term of natural inquiry are based on analysis and demonstration quia.

Demonstration can be made in two ways: one is through the cause and is called propter quid, and this is to argue from what is prior absolutely. The other is through the effect and is called a demonstration quia; this is to argue from what is prior relatively only to us. When an effect is better known to us than its cause, from the effect we proceed to the knowledge of the cause. And from every effect the existence of its proper cause can be demonstrated, so long as its effects are better known to us; because, since every effect depends upon its cause, if the effect exist, the cause must pre-exist. Hence the existence of God, in so far as it is not self-evident to us, can be demonstrated from those of His effects which are known to us. [S.Th., I, 2, 2]

Thus, the law of evidence plays a role that is as essential in Thomistic method as it is in Cartesian method; for where there is no evidence, demonstration is impossible, since reason has no starting point in truth to use as a springboard from which to arrive at a truth as yet unknown to it. But, unlike Descartes, St. Thomas admits two kinds of evidence, which are sometimes antipodal to each other. For him, in the analytic order of discovery, reason never uses truth that is evident in itself as its starting point, but always truth that is evident to us. But what is most evident to man, in explaining the concrete real, is sensible evidence, because the intellect progressively discovers its natural object by starting from the sense, and it is at the heart of material things that it seeks the being most immediately able to measure its judicative activity, or, rather, the first truths by which it is nourished. The starting point for the mind’s inquiries is therefore immediate evidence concerning the being that is least intelligible in itself—material being—and concerning what is least intelligible in material being-material accidents. Thus, analytic method is, in some way, a substitute for Cartesian deduction, but instead of having its point of departure in evidence absolute in itself, it starts from that which is evident relative to the human intellect, i.e., in evidence where sensory knowledge plays a primary role. This conforms to the general principles of Thomistic epistemology, for which human knowledge cannot be explained without the continual interplay of all our cognitive sensory powers. And the term of this process is the discovery of a new truth, known not in its nature but in its existence.

(b) Synthesis as a method of discovering mediate truth. Like all discursive activity, of which it is an aspect, synthesis requires, as starting point for its movement, an evidential truth from which it draws a hitherto unknown truth, not merely the successive consideration of two truths.

In our knowledge there is a twofold discursion. One is according to succession only, as when we have actually understood anything, we turn ourselves to understand something else; while the second mode of discursion is according to causality, as when through principles we arrive at knowledge of conclusions... This second mode of discursion presupposes the first, for whosoever proceeds from principles to conclusions does not consider both at once... because to advance thus is to proceed from the known to the unknown. Hence it is manifest that when the first is known, the second is still unknown; and thus the second is known not in the first but from the first. [S.Th., I, 14, 7]

What then is the, typical aspect by which synthesis differs from analysis, since both are rational or discursive methods for acquiring knowledge of the existence of a new truth starting from an anterior truth that is its source? The distinctive aspect by which synthesis differs from analysis as an order of discovering mediate truth is the very nature of the evidence the former uses as principle and point of departure.

In every inquiry one must begin from some principle. And, if this principle precedes both in knowledge and in being, the process is not by way of analysis but by way of synthesis; for to proceed from cause to effect is to proceed in a synthetic way, since causes are more simple than effects. [S.Th., I-II, 14, 5]

The comprehension of a really existing causal order is therefore at the beginning of the discovery of the existence of a new truth, for this truth is nothing but the measuring of our mind by the ipsum esse of a known effect as such. Setting aside the domain of local movement, thus setting aside all that characterizes modern science, we have seen that there are twelve different modes of catalyzing the multiplicity of the real, that is, of linking up the diversity of things to their principle. These twelve modes are reducible to four categories of principles: those which explain the complexity of the nature and of the thing existing as such, i.e., matter and form on the one hand, essence and existence on the other; and those which account for becoming and the existing of real things in becoming, and these are the efficient, exemplar, and final causes.

This being the case, in its march toward truth the synthetic method can take as its starting point one or the other of these causes whose evidence will he the source of a new and previously unknown truth.

Reason sometimes advances from one thing to that which is other in reality, as when the demonstration is through external causes... by synthesis indeed when we go from causes to effects, for causes are simpler than effects and exist more unchangeably and uniformly.... Sometimes, however, reason advances from one concept to that which is other according to reason, as when we proceed according to intrinsic causes; by synthesis indeed when we go from most universal forms to more particular ones. [In lib. De Trin., 6, 1]

To the reader familiar with the Scholastic categories, the meaning of this doctrinally massive text is not ambiguous, for he knows that the relations of material, formal, efficient, exemplar, and final causality are realities belonging properly to our universe and that, by means of these relations of diverse causality, this universe escapes the hurly-burly of chance and is a perfectly unified complex of its parts, just as the complexity in a being derives its unity from intrinsic causal bonds. But to a mind trained in scientific methods, this text is not so clear, for in this context the notion of cause has lost all its metaphysical meaning to become synonymous with succession: cause has become identified with law. Such a mind interprets merely mathematical classifications of physical laws in terms of explanation, of why, that is, in a vocabulary of causality. In other words, the expression causal order has become ambiguous for contemporary minds because it is called upon to signify two completely opposite realities, either the image of the world that science constructs by its laws, or the ontological universe itself with the real relations that exist between its different parts, a universe that philosophy [and complete science] tries to understand and to explain by reference not to its mathematicized image but to its existential mode. True, an attempt is being made to remove this ambiguity. Every scientific endeavor that ceases to be “legal” in order to become explanatory is branded as vicious and parasitic, but the confusion between legality and causality continues in the modern mind and makes incomprehensible any philosophical explanation that eschews legality to dedicate itself exclusively to causality. Yet St. Thomas well understood the difference between the two when he said that no hypothetical statement could serve as starting point for genuine knowledge, that is, for knowledge of the causal order. But he recognized the legitimacy of legality for describing phenomena whenever it unified them into a harmonious whole. He himself cites an instance of opposition between causality and legality, in the case of Greek astronomical theory:

Reasoning may be brought forward for anything in a twofold way: firstly, for the purpose of furnishing sufficient proof of some principle; as in natural science sufficient proof can be brought to show that the movement of the heavens is always of a uniform velocity.... Reasoning is employed in another way, not as furnishing sufficient proof of a principle but as showing how the remaining effects are in harmony with an already posited principle; as in astronomy the theory of eccentrics and epicycles is considered as established because thereby the sensible appearances of the heavenly movements can be explained; not however as if this proof, were sufficient, since some other theory might explain them. [S.Th., I, 32, 1]

Thus, we must have an extremely precise notion of what is meant by causality in philosophy, as opposed to scientific legality. The latter rests entirely upon the principle of identity, upon a sort of identifying reduction between the law and its phenomena, whereas philosophical causality rests upon the otherness and even the diversity between an effect and its cause. The difference between legality and causality is vividly brought out by comparing their respective relations with phenomena and with effects. Thus, while physical phenomena remain identical, laws change with the progress of science; disappearance or change in a cause, however, necessarily entails disappearance or change in the effect. Furthermore, legality is an invention of the mind, it is an order set up by the mind to bring unity into phenomena, whereas causality is an order that the mind contemplates but does not make. It is constitutive of the most inward structures of the universe, whose reality is to be participation, that is, a total gift of Him who is Being by essence and therefore Cause by essence.

Consequently, when we speak of causal order in philosophy, we are at the very heart of the object of philosophy, i.e., of being in all its modes. What we call intrinsic causes are none other than that which defines reality as composite, whether this composition is that of a nature from matter and form or that of a being from essence and esse. It is the principle of identity, in the philosophical sense of this word, that simultaneously governs the distinction between compositive elements and their unity as nature and as being. As for extrinsic causes, they link accidents to substances and substances to each other in a hierarchy of perfection according to nature and existing; ultimately they blend into an absolute unity, when absolute efficiency, exemplarity, and finality meet in Him who is Being. This is the depth of the real that must be sounded if we are to grasp what St. Thomas means by causal order, and what he means when he says that synthesis starts from the evidence of causes in order to come to the evidence of effects.

It could he objected that if the synthetic order of discovery works at this depth of the real, there are few opportunities to use it, for when do we know beings by their causes? The objection is valid, for we must admit that demonstrations concerned with the proper causes of singular beings are very few and far between. Science, however, is not much better suited to know the singular scientifically, for it exists [in part] only by virtue of statistical laws, and the singular as such has for science neither value nor existence. But the synthetic order of discovery has absolute efficacy when it comes, for example, to defining mobile being as such, and to linking up all the properties of this reality in its mutability, its mobility, its temporality, and its localization—as can be seen in the Physics of Aristotle. The same is true for living being and the specific properties of the different modes of life as such. Finally, in questions dealing with man and being as being, demonstration can really be an extraordinary instrument for the discovery of the nature of man and the properties flowing from this nature.

The synthetic order of discovery is, in short, the inverse of the process used to know natures. Whereas we know the latter by starting from accidents that lead us to natures by a sort of reditus, in demonstration there is a kind of exitus of accidents of which substances are causes, or an exitus of creatures of which God is the Creator. Such is the second procedure for discovering mediate truth. Like the first, it is a consequence of the weakness of our intellect that becomes reason-knowledge by mode of movement—only because it is ill equipped by nature to fulfill its function as intellect or intuitive power. More perfect than the first order of discovering truth, the synthetic order, because of its very perfection, has a more restricted use, since it is closer to the intellectual processes than is the analytic order. For synthesis begins with an intuition of causes in order that it may intuit effects, whereas analysis goes from the existence of effects to that of causes. And this is why the synthetic order belongs rather to wisdom than to natural philosophy, as we shall see in the following section and in the conclusion of our treatise on epistemology.

Section III: Value Judgment upon Mediate Truth, or Assent to Conclusions

Analysis and synthesis, as instruments for discovering new or mediate truth, are instruments for the enrichment of the human intellect, since truth is its good and its perfection, just as error is its evil and its corruption.

The good of our understanding is the knowledge of truth. Accordingly, those habits by which the understanding is perfected for the knowledge of truth are called virtues... because they make the act of understanding good. Falsity, on the other hand, is not only lack of truth, but also a corruption of it... Consequently, just as truth is the good of the understanding, so that which is false is its evil.

But it is not enough to possess riches; we must assess their value, for some riches can be destroyed as easily as wood by fire. The market place of truth is like the stock exchange: it includes more and less secure values, and bankruptcy is always possible if stocks are bought without full knowledge of their soundness or security. All truths do not, in fact, possess the same guarantees of stability, for the true can be either contingent or necessary, and only necessary truth is sufficiently well guaranteed to allow the intellect to rest in it as in an immutable good.

Since the act of our understanding is good because it considers the true, it must be impossible for a habit existing in the understanding to be a virtue unless it is such that, by it, one infallibly speaks the truth. For this reason, opinion is not an intellectual virtue, whereas scientific knowledge and understanding of principles are. [De veritate, 14, 8]

Therefore, once mediate truth is discovered, it must be evaluated, so as to arrange the hierarchy of its value as a good and to ascertain that the intellect’s new treasure is safe from the gnawing worm of contingence or fallibility. We know that in Thomism the act by, which we judge the value and infallibility of truths already possessed is called assent. We also know that the intellect is compelled to assent only when faced with an infallible truth so evident that it cannot reasonably be denied. In immediate truths, evidence presents no difficulty because the link between subject and predicate is the object of intuition and requires no proof or witness.

Yet those things are said to be present to the understanding which do not exceed its capacity, so that the gaze of the understanding may be fixed on them. For a person gives assent to such things because of the witness of his own understanding and not because of somebody else’s testimony. [De veritate, 14, 9]

But, by definition, mediate truths are not of themselves evident to the intellect; their very lack of evidence constrains the intellect to that process of inquiry which aims to discover them. The question therefore is: How can a truth, possessing no claim to the immediate evidence that alone forces assent, become the object of assent? This is the last aspect of the discourse on Thomistic method, which, after having set up two critical approaches for the discovery of mediate truths, brings in a third to evaluate these discovered truths by projecting upon them the light of first evidential principles. In so doing, it gives them a share in the intelligibility of these first principles and thereby a share in their compulsive power upon the mind. We. shall now make a brief study of this last phase of Thomistic epistemology, first considering the vocabulary that indicates its existence in the works of Aquinas, and then describing the nature of this critical method of mediate truth.

A. THE VOCABULARY OF ASSENT TO MEDIATE TRUTHS

St. Thomas always characterizes the act of assent by its opposition to the activity that grasps or discovers truth. Although he uses many words to signify the perception of the existence of truth, he always uses the same terms for the act of evaluating discovered truth, expressing its infallibility by reference to its nature. These terms are as follows: judicare, dijudicare, via judicii, via judicandi. Here are two important texts on this subject:

Now the reason is speculative and practical, and in both we find apprehension of truth, which pertains to its discovery, and judgment on the discovered truth. Accordingly, for the apprehension of truth, the speculative reason is perfected by understanding.... In order to judge rightly, furthermore, the speculative reason is perfected by wisdom. [S.Th., I-II, 68, 4]

Human reasoning, in the order of discovery or inquiry, proceeds from certain things absolutely understood, namely first principles; and again, in the order of judgment (via judicii), it returns, by analysis, to first principles, in the light of which it examines what it has found. [S.Th., I, 79, 8]

But this via judicii, which is opposed to the via inventionis studied above and which terminates in assent, includes particular procedures of the mind, which Aquinas expresses by the words examinare, examinatio.

Similarly the movement of reason would not reach anything certain unless there were an examination of that which it came upon through discursive movement of the mind. This examination proceeds to first principles, the point to which reason pursues its analysis... [De veritate, 15, 1]

We do find a circle in the knowledge of the soul.... The circularity is observed in this, that reason reaches conclusions from principles by way of discovery, and by way of judgment examines the conclusions which have been found, analyzing them back to principles... [De veritate, 10, 8, ad 10]

All speculative knowledge is derived from some most certain knowledge concerning which there can be no error. This is the knowledge of first general principles, in reference to which everything else which is known is examined, and by reason of which every truth is approved and every falsehood rejected. [De veritate, 16, 2]

There is, finally, another term in this lexicography whose importance is the greater because it indicates the nature of this act by which the mind examines the mediate truths discerned by reason. This term is resolutio, resolvendo, which we meet again here, no longer in a context of the discovery of truths, but as the process of evaluation used by the human mind to sift its harvest of truths and to separate the pure wheat of necessary truth from the straw of contingent and mutable truth. Now it remains for us to examine the functioning of this evaluation of mediate truths that is analysis in the order of judgment or assent.

B. Analysis as a means of assent to mediate truths

To judge is not a property of reason through which it can be distinguished from understanding; for understanding, too, judges that this is true and that false. But judgment is referred to reason and comprehension to understanding to this extent: that in us judgment commonly takes place through analysis (per resolutionem) into principles, whereas direct comprehension of truth takes place through understanding. [De veritate, 15, 1, ad 3]

We must not forget that this last chapter in our epistemology is concerned with infallible knowledge of mediate truth, the only truth whose infallibility is called into question, since it alone is produced by the human reason, first or immediate truths being the spontaneous fruit of the very nature of our mind. Now, how can we know that the result of long and delicate workings of reason contains truth whose necessity is such that its negation would entail the negation of first truths? For this is the result we must achieve if the value of mediate truth is to be indisputable; the evidence of mediate truth must be experienced by the mind, must be present to it with the same cogency as that of first truths.

The whole certainty of scientific knowledge arises from the certainty of principles. For conclusions are known with certainty when they are reduced (resolvuntur) to principles. Therefore, that something is known with certainty is due to the light of reason divinely implanted within us, by which God speaks within us.... Nevertheless we would never attain the certainty of scientific knowledge... unless there were within us the certainty of the principles to which the conclusions are reduced. [De veritate, 11, 1, ad 13]

The role of analysis in the critique of the truth of conclusions consists therefore in making the evidence of the conclusion to be present to the intellect, by showing that this conclusion is essentially a participation in first evidence, a sort of attenuated luminosity Of this same evidence.

Whatever things we know with scientific knowledge properly so called, we know by reducing them to first principles which are naturally present to the understanding. In this way, all scientific knowledge terminates in the sight of a thing which is present. [De veritate, 14, 9]

How does analysis realize this kind of identification between the evidence of mediate truth and that of first principles? In other words, what is this activity of reduction or resolution to first principles? To understand its full epistemological value, as well as its essentially critical function, we must recall the definition of this activity of the mind as described in the preceding section. What characterizes it as a discursive movement is that it has as starting point the complex, the least being, the least knowable, the effect, the sign, and as goal the simple, the most being, the most knowable, the cause, the signified. Every time the mind is confronted by a mediate or concluded truth, this latter is inevitably a particularized truth, for each science possesses a particular domain that is the object of its inquiry. Since its own proper principles are particularizations of first evidences, its conclusions are necessarily still more determined than are their proper principles and, a fortiori, than first principles or evidences. This being so, who does not see that the typical task of analytical discourse is to reduce this particular evidence, which is an effect, a least knowable, a complex, to evidence that, on the contrary, has the most absolute simplicity, knowability, and causality, each and every one of which possesses the evidence of a principle, especially the evidence of non-contradiction?

To avoid long explanations about this process of reduction of mediate truth to the evidence of first principles, a reduction that compels intellectual assent, we shall illustrate this process of identification by a simplified example that will show more clearly than pages of explanation how every concluded truth can be thoroughly criticized and how, by means of this criticism, the mind can be compelled to adhere to a conclusion under pressure of its only absolute good, infallible truth as such. Let us consider the following demonstration:

The major is an absolute, although not a common, principle, for it presupposes the notion of spirituality that only metaphysical knowledge can provide. The minor is evident only after long and painful inquiry and reflection on the different activities of man, as St. Thomas admits, and as he himself shows in his treatises on man and the soul. Once the evidence of the major and minor is seen, the conclusion necessarily flows therefrom, and we have a mediate truth. Can this mediate truth force the assent of the intellect? No, as long as it is not made present to the mind with the very evidence of first principles, which alone are cogent. Therefore, this particular truth must, by process of analysis, be identified with primary evidence, and then only will the mind judge this truth, i.e., give it its assent. Let us try to effect this identification by analyzing the notions included in the conclusion. There are two, the soul and immortality.

1. The Soul. We define it in the minor as a spiritual substance, and we accept this definition since the inquiry preceding it was exhaustive and eliminated all possibility of error. To be spiritual is not to have matter, to be immaterial, and not to be material is the same as not having any quantity, for quantity is a consequence of matter. But everything that is not quantity is indivisible for divisibility presupposes the existence of parts, and the existence of parts implies the existence of quantity and, therefore, of matter. Thus, being immaterial is identical with being indivisible, and to define the soul as immaterial is to define it as an indivisible absolute.

2. Immortality. What is immortality? It is the absence of mortality, and mortality is the separability of a body and its vivifying principle. In order that a living thing be mortal, it must be composed of two principles, and of two separable principles. Thus, the concept of mortality implies, from its very notion, the idea of divisibility, and death implies not only divisibility but division in fact. If therefore, a being is divisible but never divided, he will be mortal but will not die. But if a being is indivisible because he is simple or because he completely lacks compositive parts, then he not only will not die but will be immortal by right. Immortality de jure implies indivisibility of the living being, so that to say of a being that he is immortal, or to say that he is indivisible, is to say the same thing.

Let us reconsider our conclusion now, in replacing the original terms by their synonyms; let us replace the soul by absolute indivisibility and immortality by indivisibility, and we have the following: The indivisible (the soul) is indivisible (immortal). As anyone can see, this statement is nothing but a statement of the principle of identity, a sort of application of the primary evidence: being is being. Thus, by this analytical process, we have identified a particular conclusion with primary evidence; we have reduced mediate truth to an immediate truth possessing the same characteristics of simplicity, greater knowability, and causality that are possessed by the principle of identity. Just as assent is compelled by the evidence of the principle of identity, so also can it not resist this reduction of the conclusion to the principle of identity; the mind is compelled to adhere to the conclusion that the soul is immortal.

Also, were anyone to deny this evidence verbally, his denial could be reduced to the absurd by reducing the conclusion to the principle of non-contradiction: If the indivisible is not the indivisible, being is not being, therefore being is non-being, and if being is non-being, the principle of non-contradiction is false, which reduces the intellect to the realm of the absurd.

This example establishes the meaning of the resolutio of conclusions to principles and at the same time shows us that, for St. Thomas, to know does not consist in lining up arguments one after the other and producing conclusions. These conclusions must show their identification papers as necessary and infallible truth, and only on this condition do they enter into the realm of truths forming the imperishable treasure that our intellect seeks and whose possession constitutes our human happiness.

All science puts the intellect in possession of its good, for all truth is a good for the intellect. But not every science enriches the human soul with its best good, for only that which brings it to first truth can do that. [Quodlibeta, 4, 16, ad 1]

Therefore, mediate truth must, somehow bathe in the light of first truth, in order to possess this value as beatifying perfection which it has only as intellectual end. But it cannot bathe in this evidence of first truth unless, by a movement of return, it rejoins that of which it is only a participation; for the sapiential vision of being as such is the source of all discursive activity productive of truth, and also is its last measure, since it is by being confronted with this vision that every conclusion receives its letters of credit or has its unauthenticity unmasked.

In reference to the first general principles, everything else which is known is examined, every truth is approved, and every falsehood is rejected. [De veritate, 16, 2]

There are two reasons that first truths have this function of testing, in relation to all other truths: first, because they are natural and, consequently, participate in the infallibility of the intellect considered as nature, i.e., as direct effect of divine wisdom. Furthermore, these first truths have themselves been judged by wisdom, for it belongs to the latter to define the notions that make up first principles, because wisdom has ultimate causes as its domain, that is, all things divine, God and His proper effects.

Now to know the definition of being and non-being, of whole and part and of other things consequent to being, which are the terms of which indemonstrable principles are constituted, is the function of wisdom, since universal being is the proper effect of the highest cause, which is God. And so wisdom makes use of indemonstrable principles, which are the object of understanding, not only by drawing conclusions from them, as other sciences do, but also by passing its judgments on them, and by vindicating them against those who deny them. [S.Th., I-II, 65, 5, ad 4]

Now, in analyzing first principles, we have judged them; we have shown the absolute necessity of the intellectual act in its adherence to truth. Furthermore. we have just seen that the whole structure of discursive thought and, particularly, the whole dynamism of philosophical science depend upon this sapiential vision of first principles, which are their starting point and their end. This means that, in Thomism, the whole epistemological edifice is the work of wisdom, not science, and that to wish to construct a discourse on Thomistic method by taking science as point of departure is to try to justify intellect by reason, the end by the means, the cause by the effect which amounts to seeking an absurd criterion by absurd means.

Therefore, we believe it right and opportune to conclude this treatise on Thomistic epistemology by underlining its essentially sapiential character, for by this character it stands in contrast to all modern epistemologies, both idealist and realist. Thanks to thiis character, the thought of St. Thomas has been able to achieve the mighty synthesis that surmounts both time and space, towering above science and its evolution, to remain as presently true in the twentieth century as it was at the moment of its creation.

CONCLUSION

The reader sufficiently courageous to follow our epistemological explanations to this conclusion is probably divided between two contrary impressions: one, that he has been witnessing an authentic exploration of St. Thomas’ gnosiological theory; and the other, very different, that he has found nothing here that remotely resembles a treatise in critical philosophy as the subject has been conceived since Descartes and Kant. To understand the reason for the ambiguity that beclouds the notion of Critique and to divest it forever of the scientific mask behind which the putative fathers of philosophical method have hidden it—a mask that for three centuries has hidden the true face of Critique—we must paraphrase the Gospel maxim and, “give to science what belongs to science, and to wisdom what belongs to wisdom.” Such justice has not been rendered since the fourteenth century.

During three centuries, from the fourteenth to the seventeenth, so-called wisdom denied science its liberty of method and autonomy of movement in the field of experimentation and mathematization of experimental facts. Since the seventeenth century it is philosophy that has been imprisoned by the mortal chains of scientific method. And just as philosophy gained nothing from persecuting science and its methods, so science has won nothing by its tyranny over philosophic thought. All humanity has suffered from this paralysis of the philosophic impulse, induced by repeated injections and massive doses of alleged scientific vaccine against error.

This treatise on epistemology has attempted merely to put the evangelical maxim into practice, and to distinguish the orders of knowledge so as to give philosophy what rightfully belongs to it: its proper methods and its proper objects. Now, only the sapiential part of philosophy has this self-critical power, a power that it can exert over the other aspects of human knowledge.

But wisdom has something proper to itself above the other sciences, inasmuch as it judges of them all, not only as to their conclusions, but also as to their first principles.... So both understanding and science depend on wisdom... for it contains beneath itself both understanding and science, adjudging both the conclusions of sciences and their principles. [S.Th., I-II, 57, 2, ad 1 & 2]

Since philosophical epistemology has no purpose other than to explain and justify its own typical knowledge—knowledge of its possession of things through the ultimate causes that explain this immanent possession—it evidently cannot ask either Aristotelian science or a fortiori modern science to determine its method and objects. Only a wisdom whose proper object is precisely the final causes of all things, as well as the final causes of knowledge, since the latter is a reality possessing its own ontological value—only a wisdom has sufficiently broad vision simultaneously to explain the reality of knowing and of the real thing that is the object of knowledge. Therefore, by way of conclusion, we would like to underline the sapiential character of St. Thomas’ epistemology, taking as basis the diverse methods that according to him, characterize the different aspects presented by human knowledge to the reflecting mind. A brief commentary on an essentially methodological text will terminate this work, which has, up to this point, been a long commentary on the epistemological thought and texts of Aquinas.

To the methodology of speculative sciences St. Thomas has devoted a whole question, divided into three sections: one on natural science, one on abstract science, that is, mathematics, and one on divine science or wisdom. In the first article of this question he draws a comparison between these three types of knowing by emphasizing the characteristic method of each. Here is the question as he states it:

Must we proceed according to the mode of reason (rationalibiliter) in natural science, according to the mode of learning in mathematics, and according to the mode of intellect in divine science? [In lib. De Trin., 6, 1]

To this threefold question there are three answers, each of which in substance contains all that is both common and contrary to the methodology of each of these modes of knowing. We shall comment briefly on the first two answers and linger a bit longer over the third, which with utmost clarity reveals the laws governing the structure of philosophical epistemology and its sapiential character.

A. The rational character of the method used in natural science

St. Thomas begins by distinguishing three meanings of the word rational as applied to method:

The first meaning is identified with logic, which should be expected for logic, as its name implies, is identical with the rational. The word ratio translates the Greek word logos, from which logic draws its name. Logic moreover, is defined as philosophia rationalis. Interpreted in this logical context, rational method cannot characterize natural science for that would run counter to its very nature as a particular science.

But this method of proceeding cannot belong properly to any particular science, which will fall into error unless it proceeds from its own proper principles. [Ibid.]

In its second meaning the word rational applies to dialectical method or probable reasoning, as an instrument of research directed to the discovery of truth but failing to discover it for lack of causal evidence.

Sometimes, however, the investigation of reason cannot arrive at the ultimate end, but stops in the investigation itself, that is to say, when two possible solutions still remain open to the investigator. And this happens when we proceed by means of probable arguments which are suited to produce opinion or belief but not science. In this sense, rational method is distinguished from demonstrative method. And we can proceed rationally in all the sciences this way, preparing the way for necessary proofs by probable arguments. [Ibid.]

In this context of dialectical argumentation, rational method cannot be characteristic of natural science since it is common to all the demonstrative sciences. In fact, this method is characteristic of experimental science in the modern sense of the word, in which hypothesis or law plays the same role in the explanation of phenomena that cause plays in philosophy.

Reasoning is employed in another way, not as furnishing a sufficient proof of a principle but, a principle being posited, as showing how harmoniously the effects follow this principle. As in astronomy the theory of eccentric and epicycles is considered as established, because thereby the sensible appearances of the heavenly movements can be explained; not however, as if this proof were sufficient, since some other theory might explain them. [S.Th., I, 32, 1, ad 2]

Finally, in its third sense the word rational describes the method proper to the philosophy of nature, because this aspect of our knowing corresponds to the very structure of the human mind, which is defined as reason and not as intellect or understanding. Now, what characterizes reason, as contrasted to understanding, is that it cannot intuit the substance of things without first grasping this substance’s accidents and, secondly, that its primary object is something more knowable to us which leads it to something more knowable in itself. Thus, reason knows by mode of movement, by passing from what is more known to what is less knowable. That, actually, is the exact procedure of natural philosophy, whose proofs start from effects, from signs that are more knowable to us but less intelligible in themselves, in order to grasp causes of greater intelligibility, since they explain the existence and nature of effects and signs. In so doing, the philosophy of nature proceeds by mode of movement, which is typically rational, for physical proof does not travel from one concept to another, but from a real effect to a real cause, therefore, from one reality to another.

Natural science uses a rational method in this respect, that it is characteristic of reason to move from one thing to another... for example, from the knowledge of an effect to knowledge of its cause. Nevertheless the procedure... is not to go simply from one thing to that which is other according to reason and not other in reality.... But... demonstration takes place through extrinsic causes; something is proved from one thing through another thing entirely external to it. So the method of reason is particularly observed in natural science... and it is especially characteristic of it. [In lib. De Trin., 6, 1]

Also, just as our mind is reason because it depends on sensory knowledge both to receive its proper object and to contemplate it, since it has to return to the senses as to its principle, so must the philosophy of nature terminate in the senses because the senses are the control on the accidents of material substance. Such is the nature of the methodology to be used by the philosophy of nature, according to St. Thomas.

B. The disciplinary character of mathematical method

In order to understand the exact meaning of the word disciplinabiliter and its technical character, we would have to go back too the beginnings of Christian speculation among the Fathers of the Church and observe the transformation that this word underwent at the hands of medieval thinkers. For our purposes, however, it is enough to note that in the language of St. Thomas and his contemporaries, this term designates the most direct and surest method of acquiring absolutely certain knowledge. It possesses this clarity and this certainty because its object is less complex than that of the philosophy of nature and more intelligible for us than that of wisdom or metaphysics. St. Thomas adopts Ptolemy’s statement as his own: “Mathematics alone will give the inquirer firm and unshaken certitude, namely, demonstrations carried out with unquestionable methods.

Coming from St. Thomas, this praise of mathematical method might seem strange, for he seems to be talking like the mathematician Descartes, whereas nothing in his works justifies the high esteem he bestows upon this method in comparing it with the respective methods of natural philosophy and wisdom. We might therefore ask ourselves this question: If mathematical method has such evidence and leads to such certitude, why did St. Thomas not use it to construct a “Discourse on Method” that would teach men how best to use reason in the sciences? First of all, for Aquinas, the method of each science is dictated by the object of this science; and, secondly, mathematical method is also drawn from reason as such, with this difference, that its data come from the imagination and that its term is also the imagination and not sense. Now, neither the object of a rational science in the strict sense of the word rational nor consequently its method can explain being as such or knowing as such. For it is the intellectual or intuitive character of the human mind that accounts for reason and not reason that is the source of the intellect, whose weakness and deformity it reveals.

The certitude of reason comes from the intellect, but the necessity for reason is a defect of the intellect. For beings in whom intellect possesses its full strength do not need reason but grasp truth in a simple glance, as do God and the angels. [S.Th., II-II, 49, 5, ad 2]

Since everything certain, therefore everything perfect, in rational demonstration—whether in natural philosophy or in mathematics—originates in the intellect and not in reason, and since the need for reason springs from a deficiency of intellect, we must ask the intellectual aspect of our knowing power to construct a method of knowledge, for the perfect explains the imperfect, and not vice versa. In order for a method to satisfy the requirements of our knowing power and to justify its defects, i.e., justify its need for recourse to reason and reason’s method of inquiry, this method must be intellectual and not rational; that is, it must be the fruit of wisdom and not of a science. And that is the third problem Aquinas deals with in his brief treatise on the methodology of human knowledge.

C. The intellectual character of the sapiential method

Since the distinction between science and wisdom is the characteristic note of Thomistic epistemology, being the reason for its power as well as the cause of numerous misunderstandings and misinterpretations during the centuries—since this is true, the inner opposition that constitutes the pair of terms, intellectus-ratio, must be carefully pinpointed.

Reason is related to understanding as to its source and its term. It is related to it as to its source because the human mind could not move from one thing to another unless the movement started from some simple perception of truth, and this perception is understanding of principles. Similarly, the movement of reason would not reach anything certain unless there were an examination of that which it came upon through discursive movement of the mind. This examination proceeds to first principles, the point to which reason pursues its analysis. As a result, we find that understanding is the source of reasoning in the process of discovery and its term in that of judging. [De veritate, 15, 1]

Hence, St. Thomas describes science as rationalis consideratio, whereas he calls wisdom intellectualis consideratio. Should we therefore conclude that wisdom is the source and term of all scientific knowledge? If so, what becomes of the chronological order of our acquisition of knowledge, which starts from what is best known to us and proceeds to what is most knowable in itself, therefore, which goes from the philosophy of nature to wisdom, and not the reverse?

In the beginning, the sensible effects from which the demonstrations of natural science proceed are more evident to us. But when, through them, we know the first causes, from these latter there will become evident to us the reason for the effects on which the proof of the demonstration of the fact (quia) rest. In this way natural science contributes something to divine science and nevertheless it is divine science which explains its principles. That is why Boethius places divine science last, because it is last relatively to us. [In lib. De Trin., 5, 1, ad 9]

To understand this reasoning, which at first seems contradictory, we must call to mind the two ways in which science proceeds: the one that consists in discovering the truth, and the one by which truth that has been discovered is judged. Only the second phase is scientific knowledge in its perfect state, because it gives perfect truth to the intellect.

In the acquisition of knowledge, principles and elements are not always first; for sometimes from sensible effects we arrive at the knowledge of principles and intelligible causes. But in perfect knowledge, the knowledge of effects always depends on the knowledge of principles and elements. [S.Th., I, 85, 8, ad 1]

This then is the context of perfect knowledge or knowledge by final causes in which St. Thomas’ argumentation must be understood when he makes science depend on wisdom, i.e., rationalis consideratio on consideratio intellectualis, as on its source and term; for it is wisdom that judges the principles of science, and wisdom, too, that judges the conclusions of these same sciences. Here is the way Aquinas describes the intellectual method of wisdom:

Just as we attribute a rational method to natural philosophy because it adheres most closely to the method of reason, so we attribute an intellectual method to divine science because it adheres most closely to the method of intellect. Now reason differs from intellect as multitude from unity. For it is distinctive of reason to disperse itself in the consideration of many things and then to gather one simple truth from them.... Conversely, intellect first contemplates a truth, one and undivided, and that truth comprehends a whole multitude.... Now in its process of analysis (via resolutionis), the whole consideration of reason in all the sciences terminates in the consideration of divine science. For, as we have said, reason sometimes advances from one thing to that which is other in reality. as when the demonstration is through external causes or effects.... Consequently the ultimate end of analysis in this life is when we arrive at the highest and most simple causes which are the separate substances. Sometimes, however, reason advances from one concept to that which is other according to reason, as when we proceed according to intrinsic principles.... Now what is most universal is common to all beings; and so the ultimate end of analysis in this life is the consideration of being and the properties of being as being. And these are what divine science considers, namely the separate substances and what is common to all beings. It is clear therefore that its consideration is supremely intellectual.

It also follows from this that divine science gives all the other sciences their principles, inasmuch as intellectual consideration is the starting point of rational consideration; and for this reason it is called first philosophy. [In lib. De Trin., 6, 1]

Thus, wisdom is the perfection of the human mind which, having the natural desire to know and to know through ultimate causes, can only satisfy this desire by acquiring a wisdom that gives the human intellect possession of ultimate intrinsic causes, that is, essence and existence, and of ultimate extrinsic causes—God as creator and as final term of every being and every activity of beings. But, as we have seen, the perfection of our mind lies in its participation in divine intelligence, therefore, in the simplicity of divine intuition that is supreme wisdom, because it is knowledge of all things through contemplation of supreme being. In its own way, the human mind imitates divine knowledge insofar as it needs rationalis consideratio to fill the gaps that the weakness of the intellect as such cannot fill. Human wisdom has this peculiarity, that it is a synthesis of intellectus and ratio, that is simultaneously possesses the essential perfection of the intellect and the relative perfection of rational activity; thus, wisdom holds a privileged place in the hierarchy of the human ways of knowing, because it contains them all through its power of judging the principles and conclusions of the sciences as well as its own objects. Therefore, it comes naturally within its function to assign to each type of philosophical knowledge its proper method. To ask that it beg of the subjects it rules, not by election but by nature, both permission to govern its kingdom and information about the structure of this government, is nonsense and demagoguery. Yet, this is the absurd regime that Descartes and Kant imposed on philosophy when, in the name of the clarity and certitude of mathematical or physical sciences, they conceived a rational method of knowledge to which philosophy must submit or risk extinction. They were not aware that this forced submission of philosophical thought to scientific procedure was itself an abdication and negated every possibility for metaphysics to exist as such. And the conclusion Kant came to did not justify his critique but made it manifestly clear that when reason tries to be the basis of wisdom, wisdom is inevitably doomed to destruction and death.

This is the conclusion to which we must come after having studied the problem of human knowledge through both history and philosophical reflection. The first part of our treatise sought the ultimate causes of the successive failures suffered by the critical problem during the three last centuries; the conclusion of this historical study was that the problem had been incorrectly stated at the start, precisely because science had assumed the responsibility of stating and solving it within the framework of scientific or rational reflection. Knowing the cause of these failures, we tried to state and solve the epistemological problem in the name of wisdom, by means of a sapiential, an intellectual, not a rational, method. This enabled us to define knowledge by its proper causes of immanence and objectivity without rejecting the least bit of objective reality, or discarding even the smallest of our cognitive activities. Having defined the nature of knowledge in terms of its constitutive principles, we were able to examine the specific accidents flowing from this nature, and we discovered, first, the existence of truth and the nature of the act that gives it birth. Then we discovered the different modes of truth and their opposition to error, as well as the natural and spontaneous character of the act that contemplates truth as the perfection for which our intellect is made. There remained a last problem, that of rational truth, i.e., the truth which escapes the intellect because of its native imperfection and which the intellect must seek in order to discover and evaluate its goodness and necessity. This study, too, was conducted in the light of the causes of this rational process, both that which gives it birth and that which judges its perfection. In both cases we found that the true cause was the intellect: the intellect as habitus of first principles giving rise to the rational process, and the intellect in its sapiential state being the supreme judge of rational procedures and the truths it gathers along the way. Such is the atmosphere of an epistemological treatise according to Aquinas, and such are the progressive phases in a study of human knowledge and its properties.

Here and there in his works, St. Thomas likes to repeat that stability is the work of wisdom and is its sign, restating what Aristotle had said in a humorous vein: “We do not look upon the happy [wise] man as a kind of chameleon.” A discourse on method is not better because it is up-to-date, or because it evolves with the latest advances of contemporary science, for then it does resemble a chameleon—as the history of the past three centuries has amply proved. Epistemology receives its stability from being the product of a sapiential vision of man and the universe, a vision that includes science but of which science cannot even suspect the existence, for Wisdom has Itself defined Its dwelling place: “I dwell in the highest places, and my throne is in a pillar of a cloud.” Such was and such remains the epistemology of St. Thomas. May he help us to understand it and to make it understood to those who have taken science as their guide. For if the blind be led by the blind, they will both fall into the pit. And in the realm of wisdom, science is blind.