Question Fifteen: Higher and Lower Reason


Are understanding and reason different powers in man?
Are higher and lower reason different powers?
Can sin exist in higher or lower reason?
Is deliberate pleasure in bad thoughts (delectatio morosa), which exists in the lower part of reason
through consent to the pleasure but without consent to the deed, a mortal sin?

Can venial sin exist in higher reason?


The question treats of higher and lower reason,

and in the first article we ask:

Are understanding and reason different powers in man?

[Parallel readings: III Sent., 35, 2, 2, sol. 1; S.T., I, 79, 8.]


It seems that they are, for

1. In Spirit and Soul we read: “When we want to rise from lower to higher things, first, senses come to our aid; then, imagination; then, reason; then, understanding; then, intelligence; and, in the highest place, there is wisdom, which is God Himself.” But imagination and sense are different powers. Therefore, reason and understanding are, too.

2. As Gregory says, man has something in common with every creature, and for this reason is man called all creation. However, that by which man has something in common with plants is a power of the soul, the vegetative, which is distinct from reason, the proper power of man, as man. The same is true for the senses, by which he has something in common with brute animals. Therefore, with equai reason, his understanding, which he has in common with angels, who are above man, is a power different from reason, which is proper to the human race, as Boethius says.

3. just as the perceptions of the proper senses terminate at the common sense, which makes judgments concerning them, so the discourse of reason terminates at understanding, so that judgment may be made about the things which reason has compared. For man judges of the things which reason compares when by analysis he reaches principles which are the objects of understanding. For this reason the art of judging is called analytical. Therefore, as common sense is a different power from proper sense, so understanding is different from reason.

4. To comprehend and to judge are acts requiring different powers, as is clear in proper and common sense. For common sense judges about the things which proper sense perceives. But, as is said in Spirit and Soul: “Whatever sense perceives, imagination represents, thought forms, genius investigates, reason judges, memory retains, and intelligence comprehends.” Therefore, reason and intelligence are different powers.

5. That which is simply composite relates to simple act in the same way as that which is altogether simple relates to composite act. But the divine intellect, which is simple in every way, has no composite act, but only the most simple act. Therefore, our reason, which is composite, inasmuch as it compares, does not have a simple act. But the act of understanding is simple’ “for it is understanding of things indivisible,” as is said in The Soul. Therefore, understanding and reason are not one power.

6. According to the Commentator and the Philosopher, the rational soul knows itself through a likeness. “The mind, however, in which the image resides, knows itself through itself,” according to Augustine. Therefore, reason and mind, or understanding, are not the same.

7. Powers are differentiated according to acts, and acts according to objects. But the objects of reason and understanding differ very greatly. For, as is said in Spirit and Soul: “The soul perceives bodies by sense, likenesses of bodies by imagination, natures of bodies by reason, created spirit by understanding, and uncreated spirit by intelligence.” But bodily nature differs very greatly from created spirit. Therefore, understanding and reason are different powers.

8. Boethius says: “Sense, imagination, reason, and intelligence each look on man in a different way. Sense sees figure embodied in given matter, whereas imagination judges of figure alone without matter. Reason, in its turn, transcends imagination, examining with general consideration the species which exists in singular things. Moreover, the eye of intelligence has a more lofty existence, for intelligence goes beyond the scope of the universe and by sheer force of mind surveys simple form itself.” Therefore, just as imagination is a power different from sense, since imagination considers form outside of matter, and sense sees it embodied in matter, so intelligence, which considers form absolutely, is a power different from reason, which studies the general form as it exists in individual things.

9. Boethius says: “As reasoning is related to understanding, as that which is produced, to that which exists, as time to eternity, and as the circle to its center point, so the changeable series of fate is related to the stable simplicity of providence.”“ But it is plain that there is an essential difference between providence and fate, between the circle and its center, between time and eternity, and between generation and existence. Therefore, reason, too, is essentially different from understanding.

10. As Boethius says: “Reason belongs to the human race alone, as intelligence belongs only to the divine.” But the divine and the human cannot both share in the one essence of power. Therefore, they are not one power.

11. The order of powers follows the order of acts. But to receive something absolutely, which seems to belong to understanding, is prior to comparison, which belongs to reason. Therefore, understanding is prior to reason. But nothing is prior to itself. Therefore, understanding and reason are not the same power.

12. It is one thing to consider the entity of a thing absolutely, and another to consider it as in this thing. The human soul exercises both of these considerations. Therefore, in the human soul there must be two powers, one to know the absolute entity, which is understanding, and another to know the entity in something else, which seems to be reason. We conclude as before.

13 In Spirit and Soul we read: “Reason is the sight of the mind by which it distinguishes good and evil, chooses virtues, and loves God.” These things seem to belong to the affections which are a different power from the understanding. Therefore, reason, too, is a different power from the understanding.

14. The rational is distinguished from the concupiscible and irascible. But the irascible and concupiscible belong to the appetites. Therefore, reason does, also. We conclude as before.

15. The Philosopher says: “The will is in the rational part.” But it is distinguished from understanding. We conclude as before.

To the Contrary

l. Augustine seems to say the opposite when he says: “We arrive at the image of God, which is man, in that by which he surpasses other animals, that is, in reason or intelligence. And whatever else there is of the rational or intellectual soul can be said to belong to that thing which is called mind or mental life.” From this it seems that he takes reason and intelligence as the same thing.

2. In Augustine (and in the Gloss on Ephesians [14:23], “And be renewed in the spirit of your mind,”) we read: “We should understand that man is made in the image of God in that by which he surpasses irrational animals.” But this is reason itself, mind, intelligence, or whatever other name fits it better. Therefore, it seems that reason and understanding are for Augustine different names for the same power.

3. Augustine says: “The image of that nature than which no nature is better should be sought and found in us in that than which our nature, also, has nothing better.”But the image of God is in us in the higher part of reason, as is said in The Trinity. Therefore, there is no other power in man better than reason. But, if intelligence or understanding were different from reason, they would be above reason, as is clear from the citations from Boethius and Spirit and Soul mentioned above. Therefore, in man, understanding is not a different power from reason.

4. The more immaterial a power is, the more it can extend to many things. But common sense, which is a material power, institutes comparisons of proper sensibles by distinguishing them from one another, and also has knowledge of them separately. Otherwise, it would not be able to distinguish one from another, as is proved in The Soul. Therefore, it is much more certain that reason, which is a more immaterial power, can not only compare, but also perceive things separately, a function which belongs to understanding. Thus, understanding and reason do not seem to be different powers.

5. As is said in Spirit and Soul: “The mind, capable of receiving everything, and stamped with the likeness of all things, is said to be the soul and to be a nature with a certain power and natural dignity.”1 But that which designates the whole soul should not be distinguished from some power of the soul. Therefore, the mind, which is a power of the soul, should not be distinguished from reason. Similarly, understanding, which seems to be the same thing as mind, should not be distinguished from it.

6. There is a double composition in the activity of the human soul. There is one by which it joins and divides predicate and subject, by forming propositions. The other is that by which it joins by comparing principles with conclusions. In the first composition the same power of the human soul apprehends the simple things, that is, predicate and subject, through their quiddities, and forms a proposition by joining them. For both of these are attributed to the possible intellect, according to The Soul. Therefore, with like reason there will be one power which grasps principles, a function which belongs to understanding, and which orders principles to conclusions, a function which belongs to reason.

7. In Spirit and Soul we read: “The soul is an intellectual or rational spirit.” From this it seems that reason is the same as understanding.

8. Augustine says: “As soon as something arises which is not common to us and animals, it belongs to reason.” This same thing also belongs to understanding, according to the Philosopher. Therefore, reason and understanding are the same.

9. Difference of objects in their accidental qualities does not indicate diversity of faculties. For a colored man and a colored stone are perceived by the same sensitive faculty, since it is incidental to the sensible thing in so far as it is a sensible thing, to be a man or a stone. But the objects which are ascribed to reason and understanding in Spirit and Soul, that is, “created spirit” and “corporeal nature,” do not differ, but agree, in their essential character as object of knowledge. For, just as a created incorporeal spirit is intelligible because it is immaterial, so, too, bodily natures are objects of understanding only in so far as they are separated from matter. Thus, both of these, in so far as they are known, share in one character of cognoscibility, the character of immateriality. Therefore, reason and understanding are not different powers.

10. Every power that compares two things with each other must have knowledge of each separately. Hence, the Philosopher proves.that in us there must be one power which knows “white and sweet” because we can distinguish between them. But, just as one who distinguishes between different things relates them to each other, so also, he who compares them relates one to the other. Therefore,, it also belongs to the power which compares, namely, reason, to know something separately, which is an activity of understanding.

11. It is more noble to compare than to be compared, just as it is more noble to act than to be acted upon. But a thing is understood and compared through the same thing. Therefore, the soul, also, understands and compares through the same thing. Therefore reason and understanding are the same.

12. One habit does not exist in different powers. But it is possible for us to compare and perceive something separately by the same habit. Thus, faith, which perceives a thing separately, in so far as it clings to first truth, also compares, to the extent that by a sort of reasoning it sees first truth mirrored in creatures. Therefore, it is the same power which compares and which perceives something separately.


For a clear understanding of this question we must investigate the difference between reason and understanding. We must bear in mind that, according to Augustine, just as among corporeal substances there is an orderly disposition, according to which some are said to be higher than others and have control over them, so, too, among spiritual substances there is a certain orderly disposition.

The difference between higher and lower bodies seems to lie in this, that the lower bodies reach the perfection of their existence through the movement of generation, change, and increase. This is obvious in stones, plants, and animals. Higher bodies, however, have the perfection of their existence according to their substance, power, quantity, and figure immediately in their very beginning without any movement. This is obvious in the sun, moon, and stars. The perfection of spiritual nature, however, lies in the cognition of truth. Consequently, 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. This is the case with angels, and for this reason they are said to have godlike understanding. 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 humar souls. And this is why angels are called intellectual substances, wherea souls are called rational substances.

Understanding seems to indicate simple and absolute knowledge. And one is said to understand (intelligere) because in some sense he reads (legit) the truth within (intus) the very essence of the thing. Reason, on the other hand, denotes a transition from one thing to another by which the human soul reaches or arrives at knowledge of something else. For this reason, Isaac says that reasoning is the progress of the cause to the thing caused.

Now, all movement proceeds from what is at rest, as Augustine says. For rest is the term of motion, as is said in the Physics. Thus, movement is related to rest as to its source and its term, as is reason, also, which is related to understanding as movement to rest and generation to existence, as is clear from the citation from Boethius given above. It is related to understanding as to its source and its term. It is related to it as 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.

Consequently, although the knowledge proper to the human soul takes place through the process of reasoning, nevertheless, it participates to some extent in that simple knowledge which exists in higher substances, and because of which they are said to have intellective power. This is in keeping with the rule which Dionysius gives, that divine wisdom “always joins the limits of higher things to the beginnings of the lower things.” This is to say that the lower nature at its highest point reaches something of that which is lowest in the higher nature.

Dionysius also points out this difference between angels and souls when he says: “From divine wisdom the intellectual powers of angelic minds have pure and good acts of understanding, not gathering divine knowledge from divisible things or the senses or extended discussions, but uniformly understanding the intelligible things of God. 1134Later, he adds about souls: Therefore, because of the divine wisdom, souls have rationality, too, “but spread out, circling about the truth of existing things, by the diversity of division falling short of unitive minds. But through the reduction of many things to one by reflection souls are held worthy of acts of understanding equal to those of angels, in so far as this is proper and possible to SOUIS.”He says this because that which belongs to a higher nature cannot exist in a lower nature perfectly, but only according to a slight participation. Thus, in sensitive nature there is not reason, but only a participation of reason inasmuch as brute animals have a kind of natural prudence, as appears plainly in the Metaphysics.

However, what is thus shared is not held as a possession, that is, as something perfectly within the power of the one who has it. In this sense it is said in the Metaphysics that knowledge of God is a divine and not a human possession. As a result, no power is assigned for that which is held in this manner. Thus, brute animals are not said to have any reason, although they share to some degree in prudence. But this exists in them according to a natural [instinctive] judgment. Similarly, there is no one special power in man through which he gets knowledge of truth simply, absolutely, and without movement from one thing to another. Such perception of truth is in man through a natural habit, which is called understanding of principles. Accordingly, there is no power in man separate from reason which is called understanding. Rather, reason itself is called understanding because it shares in the intellectual simplicity, by reason of which it begins and through which it terminates its proper activity. For this reason, the proper act of understanding is attributed to reason in Spirit and Soul. And that which is proper to reason is given as the act of reason, where it says that reason is the sight of the soul by which it looks at the true through itself; reasoning, however, is the investigation of reason.

Even if we conceded that it were properly and completely fitting for us to have some power for simple perception and independent knowledge of the truth which is in us, it would not be another power than reason. This is clear from what follows, for, according to Avicenna, different acts indicate a difference of powers only when they cannot be referred to the same principle. Thus, in physical things, to receive and to retain are not reduced to the same principle, but the former is referred to the wet and the latter to the dry.

Therefore, imagination, which retains bodily forms in a physical organ, is a different power from sense, which receives these forms through a physical organ. However, the act of reason, which is to move from one thing to another, and the act of understanding, which is to grasp truth directly, are related to each other as generation to existence and movement to rest. But to be at rest and to be moved are reduced to the same principle in all things in which both are found. For a thing is moved to a place through the same nature through which it rests in a place. And that which is at rest and that which is moved are like perfect and imperfect. Hence, the power which moves in thought from one thing to another and the power that perceives truth are not different powers, but one power which knows truth absolutely, in so far as it is perfect, and needs movement in thought from one thing to another, in so far as it is imperfect.

Consequently, in us, reason, taken strictly, can in no way be a power different from understanding. But, sometimes, the cogitative power, which is a power of the sensitive soul, is called reason, since it makes comparisons between individual forms, just as reason, properly so called, does between universal forms, as the Commentator says. This has a definite organ, the middle cell of the brain. And this reason is, without doubt, a power different from understanding. But we are not speaking of this at present.

Answers to Difficulties

1. Spirit and Soul is not authentic and is not believed to belong to Augustine. Nevertheless, in support of what it says, one can say that in what he said the author did not intend to distinguish powers of the soul, but to show the different steps by which the soul advances in knowledge, so that through the senses it knows forms in matter, through imagination it knows accidental forms without matter, but with the conditions of matter. Through reason it knows the essential form of material things without the individual matter. From this it rises higher in the possession of some kind of knowledge of created spirits, and, thus, is said to have understanding, since spirits of this sort have prior knowledge of substances which exist entirely without matter. From this it goes even further to some knowledge of God himself, and thus is said to have intelligence, which gives the proper name of the act of understanding, since to know God is proper to God, whose understanding is His intelligence, that is, His act of understanding.

2. As Boethius says: “The higher power embraces the lower, but the lower in no way rises to the higher.” Hence, a higher nature can do fully what belongs to the lower, but it cannot perform fully what belongs to one still higher. Therefore, the nature of the rational soul has powers for the things that belong to sensitive and vegetative nature, but not for the things that belong to the intellectual nature which exists above it.

3. Since, according to the Philosopher, common sense perceives all sensibles, it must be drawn to them according to one common character; otherwise it would not have one object of its own. None of the proper senses can attain to this common character of object. Reason, on the other hand, reaches direct understanding as its term when, for example, the movement of reason concludes at science. Consequently, it is not necessary that in us understanding be a different power fromm reason, as common sense differs from the proper senses.

4. 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 and the comprehension of intelligence are referred to reason to this extent, that in us judgment commonly takes place through analysis into principles, whereas direct comprehension of truth takes place through understanding.

5. That which is altogether simple completely lacks composition. But simple things are preserved in composite things. Thus it is that what belongs to the composite, in so far as it is composite, is not found in what is simple. Accordingly, a simple body does not have taste, which follows upon mixture. But compound bodies have the things which belong to simple bodies, although in an inferior manner. Thus, hot and cold, light and heavy, are found in compound bodies. Therefore, there is no composition in the divine understanding, which is entirely simple. But our reason, although it is composite, can enter upon simple act and composite act, either as it puts subject and predicate together or joins principles in order to arrive at a conclusion, because there is something of the nature of the simple in it, as the model is in its image.

Therefore, in us, it is the same faculty which knows the simple quiddities of things, which forms propositions, and which reasons. The last of these is proper to reason, as reason; the other two can also belong to understanding, as understanding. Hence, the second is found in angels, since they know through many species, but only the first is in God, who und6rstands all things, simple and composite, by knowing His own essence.

6. In some sense the soul knows itself through itself, inasmuch as to know is to possess in itself knowledge of itself, and in some sense it knows itself through a species of an intelligible object, in so far as knowing implies thinking and distinguishing of self. Thus, the Philosopher and Augustine are speaking of the same thing. Hence, the conclusion does not follow.

7. Such difference of objects cannot diversify faculties, because it is based on accidental differences. This has been proved above. Bodily nature is thus given as the object of reason, because it is proper to human knowledge to begin from sense and phantasm. For this reason, the gaze of our understanding, which is properly called reason, inasmuch as reason is proper to the human race, first fastens on the natures of sensible things. From this it rises higher in its knowledge of created spirit, which is more within its competence according to its participation of higher nature than according to that which is proper and perfectly fitted to it.

8. Boethius intends intelligence and reason to be different cognoscitive powers, not of the same subject, but of different subjects. Thus, he intends reason to belong to man, and so he says that it knows general forms existing in individual things, since human knowledge properly concerns forms drawn from the senses. Moreover, he intends intelligence to belong to higher substances, which in their first glance apprehend completely immaterial forms. Accordingly, he does not intend that reason should ever reach that which belongs to intelligence, since we can never in the weakness of this knowledge attain to sight of the quiddities of immaterial substances. However, we will do this in heaven when we will be made godlike through glory.

9. In so far as reason and understanding are in different beings, they are not the same power. But the present question concerns them in so far as both exist in man.

10. This reasoning proceeds correctly for acts which belong to different powers. But one power may have different acts, one of which is before the other. Thus the act of possible intellect is to understand essence and to form propositions.

11., The soul knows both, but through the same power. Nevertheless, it seems proper to the human soul, as rational, to know being in this thing. But to know being simply seems to belong rather to the higher substances, as is clear from the passage cited above.

12. To love God and to choose virtues are attributed to reason, not because they belong to it directly, but in so far as the will is attracted to God as its end, and to virtues as means to that end by the judgment of reason. It is in this way, too, that rational is distinguished from the irascible and the concupiscible, since we are inclined to action by the judgment of reason or by passion, which is in the irascible or concupiscible parts. The will is also said to be in reason inasmuch as it is in the rational part of the soul, just as memory is said to be in sense since it is in the sensitive part of the soul, and not because it is the same power.

13-14. The solution to the thirteenth and fourteenth difficulties is clear from what has been said.


Q. 15: Higher and Lower Reason


In the second article we ask:

Are higher and lower reason different powers?

[Parallel readings: II Sent., 24, 2, 2; S.T., I, 79, 9.]


It seems that they are, for

1. As Augustine says, the image of the Trinity is in the higher part of reason, but not in the lower. But the image of God in the soul is made up of the three powers. Therefore, lower reason does not belong to the same power or powers as higher reason. Thus, they seem to be different powers.

2. Since a part is taken with relation to the whole, it is in the same genus as the whole. But the soul is called only a potential (potentialis) whole. Therefore, the different parts of soul are different powers (potentiae). But higher and lower reason are given by Augustine as different parts of reason. Therefore, they are different powers.

3. Everything eternal is necessary and everything temporal and subject to change is contingent, as appears from the Philosopher. But the Philosopher calls scientific the part of the soul which deals with necessary things, and reasoning, or conjectural, the part which deals with contingent things. Therefore, since, according to Augustine, higher reason embraces eternal things and lower reason administers temporal and perishable things, it seems that the reasoning is the same as lower reason and the scientific is the same as higher reason. But the scientific and reasoning are different powers, as the Philosopher also clearly shows. Therefore, higher and lower reason are different powers.

4. The Philosopher says that we must distinguish different powers of the soul for those things which are generically different, since every power of the soul which is limited to some genus is limited to it because of some likeness. Thus, the very diversity of objects according to genus bears witness to diversity of powers. But that which is eternal and that which is corruptible are entirely different generically, since corruptible and incorruptible do not belong to the same genus, as is said in the Metaphysics. Therefore, higher reason, whose object is eternal things is a different power from lower reason, which has perishable thing for its material object.

5. Powers are distinguished through acts, and acts through objects. But truth to be contemplated is a different object from good to be done. Therefore, higher reason, which contemplates truth, is a different power from lower reason, which is occupied with the good.

6. That which is not one in itself is much less one when compared with something else. But higher reason is not one power, but several, since the image which consists of the three powers exists in it. Therefore, it cannot be said that lower and higher reason are the one power.

7. Reason is more simple than sense. However, in sense we do not find that the same power has different functions. Therefore, in the intellective part one power is much less able to have different functions. But higher and lower reason “are double in their functions,” as Augustine says. Therefore, they are different powers.

8. Whenever things which are not reduced to the same principle are attributed to the soul, we must assign different powers in the soul according to this difference. Thus, imagination is distinguished from sense according to reception and retention. But the eternal and the corruptible cannot be reduced to the same principle. For, as is proved the Metaphysics, the proximate principles for corruptible and incorruptible things are not the same. Therefore, they should not be attributed to the same power of the soul. Thus, higher and lower reason are different powers.

9. Augustine says” that through the three that co-operated in man’s sin—man, woman, and serpent—three things in us are indicated, namely, higher and lower reason and sensuality. But sensuality is a different power from lower reason. Therefore, lower reason, too, is different from higher reason.

10. One power cannot at the same time sin and not sin. But, sometimes, lower reason sins when higher reason does not, as is clear from Augustine. Therefore, lower reason and higher reason are not one power.

11. Different perfections belong to different subjects of perfection, since a proper act requires a proper power. But habits of the soul are perfections of its powers. Therefore, different habits belong to different powers. But, according to Augustine, higher reason is assigned for wisdom and lower reason for scientific knowledge, and these two arc different habits. Therefore, higher and lower reason are different powers.

12. Every power is perfected through its act. But diversity of acts leads to or manifests diversity of powers. Therefore, wherever there is diversity of acts, we should conclude to diversity of powers. But higher and lower reason have different acts, since “they are double in their functions,” as Augustine says. Therefore, they are different powers.

13. Higher and lower reason differ more than the agent and the possible intellect, since we see that the act of the agent and the possible intellect concern the same intelligible thing. But, as has been said, the acts of higher and lower reason do not concern the same thing, but different things. However, the agent and the possible intellect are different powers. Therefore, higher and lower reason are, too.

14. Everything that is drawn from something differs from it, for nothing is its own cause. But lower reason is drawn from higher reason, as Augustine says. Therefore, it is a different power from higher reason.

15. Nothing is moved by itself, as is proved in the Physics..But higher reason moves lower reason in so far as it directs and governs it. Therefore, higher and lower reason are different powers.

To the Contrary

1. Different powers of the soul are different things. But higher and lower reason are not different things. Consequently, Augustine says: “When we discuss the nature of the human mind, we are talking about one thing. And we divide it into the two which we have mentioned only by reason of its functions.”“ Therefore, higher and lower reason are not different powers.

2. The more immaterial a power is, the more it can extend to many things. But reason is more immaterial than sense. Yet, by the same sensitive power, sight, for example, we discern eternal things, either incorruptible or perpetual, namely the heavenly bodies, and corruptible things, as these lower things around us. Therefore, it is the same power of reason which contemplates eternal things and administers temporal things.


Before we can explain this question we have to know two things: how powers are distinguished, and how higher and lower reason differ. From these two we will be able to clarify the third point, which is the subject of our present inquiry, namely, whether higher and lower reason are one power or different powers.

We must bear in mind that diversity of powers is determined according to acts and objects. However, some” say that this is to be understood in the sense that diversity of acts and objects is only a sign of diversity of powers and not its cause. And others say that diversity of objects is the cause of diversity of powers in passive powers, but not in active powers.

But, if we study the matter carefully, we find that in both types of powers acts and objects are not only signs of diversity, but in some way causes of it. For every thing which has existence only because of some end has its manner determined for it from the end to which it is ordained. Thus, a saw has this kind of form and this kind of matter in order to be suitable for its end, which is to cut. But every power of the soul, whether active or passive, is ordained to act as to its end, as is clear in the Metaphysics. Hence, every power has a definite manner and species by reason of which it can be suitable for such an act. Therefore, powers are diversified because the diversity of acts required different principles from which to elicit acts. Moreover, since object is related to act as its term, and acts are specified by their terms, as is plain in the Physics, acts must also be distinguished according to their objects. Therefore diversity of objects brings about diversity of powers.

Diversity of objects, however, can be regarded in two ways: according to the nature of things and according to the diverse intelligible character of the objects. Diversity according to the nature of things appears in color and taste; diversity according to intelligible character of object, in the good and the true. Moreover, since powers which are acts of definite organs cannot extend beyond the disposition of their organs (for one and the same physical organ cannot be suitable for knowledge of all natures), it is necessary that powers which are attached to organs be limited to certain natures, that is, to physical natures. For activity which is exercised through a physical organ cannot go beyond physical nature.

However, since there is something in corporeal nature in which all bodies agree, and something in which different bodies are diversified, it will be possible to make one power attached to the body suitable for all bodies according to that which they have in common. Thus, there is imagination for all bodies in so far as they share in the character of quantity, figure, and the things which follow on these. Hence, it extends not only to physical objects, but also to mathematical objects. Similarly, there is common sense in so far as in all the physical bodies, to which alone it extends, there is a force which is active and productive of change [in the sense].

Some powers, however, are adapted to those aspects in which bodies are diversified by reason of a difference in the mode of producing change [in the sense]. Thus, sight relates to color, hearing to sound, and so on for the other senses. From the fact that the sensitive part of the soul uses an organ in its activity two things follow: first, a power referring to an object common to all beings cannot be attributed to it, for this would immediately transcend physical reality; second, it is possible to find in the sensitive soul powers which differ according to the different nature of the objects because of the disposition of the organ, which can be suited to this or that nature.

But the part of the soul which does not use a physical organ in its activity does not remain limited, but is in a sense infinite, in so far as it is immaterial. Therefore, its power extends to an object common to all beings. Hence, the object of understanding is said to be “something” (quid), which is found in all classes of beings. For this reason, the Philosopher says: “Understanding is that by which one does all things and by which one becomes all things.” Consequently, it is impossible to distinguish different powers in the intellective part according to different natures of the objects. We can do so only according to the different character of the object, that is to say, in so far as the act of the soul is directed to one and the same thing according to different relations at different times. Thus, goodness and truth in the intellective part distinguish understanding and will. For understanding is directed to intelligible truth as to a form, since it must be informed by that which is understood, and [the will] is directed to goodness as to an end.

For this reason, the Philosopher says that truth is in the mind and good in things, since form is inside and end is outside. Moreovex, form and end do not perfect a thing for the same reason. Thus, goodness and truth do not have the same character of object.

It is in this way, too, that the understanding is divided into agent and possible intellect. For something is not an object for the same reason when it is in act and when it is in potency, or when it acts or is acted upon. For what is actually intelligible is the object of possible intellect and, as it were, acts upon it so that by the actually intelligible it proceeds from potency to act. But the potentially intelligible is the object of agent intellect, in so far as by reason of the agent intellect it becomes actually intelligible.

Therefore, it is clear how powers can be distinguished in the intellective part. And higher and lower reason are distinguished in this way. There are certain natures higher than the rational soul, and certain natures lower. But, since everything that is understood is understood in the manner of the one understanding, in the rational soul the act of understanding things above the soul is lower than the things understood; but for things beneath the soul there is in the soul an act of understanding which is higher than the things themselves, since the things have a more noble existence in the soul than they do in themselves. Thus, the soul has a different relation to both types of things, and from this the different functions are derived. For it is called higher reason in its reference to higher natures, either as contemplating their nature and truth in themselves, or as receiving from them intelligible character and a kind of model for activity. It is called lower reason in so far as it is directed to lower things either to perceive them through contemplation or to manage them through activity. Both types of nature, however, the higher and the lower, are perceived by the human soul in their common character of intelligible, the higher in so far as it is immaterial in itself, and the lower in so far as it is divested of matter through the activity of the soul.

From this it is clear that higher and lower reason are not different powers, but one and the same power which is related differently to different things.

Answers to Difficulties

1. As we have said in the question on the mind, we see that the image of the Trinity in the soul is in the powers as in its root, but in its fullness it is in the acts of the powers. It is in this latter respect that the image is said to belong to higher and not to lower reason.

2. A part of a power does not always denote a distinct power, but, sometimes, a part of a power is taken according to part of the objects in so far as the virtual division of quantity is considered. Thus, if someone can carry one hundred pounds, one who can carry only fifty pounds is said to have part of that power, although the power is specifically the same. It is in this sense that higher and lower parts are called parts of reason in so far as they are directed to part of the objects to which reason, as the term is generally used, refers.

3. The scientific and the reasoning or conjectural parts are not the same as higher and lower reason, since we can have necessary considerations, which belong to the scientific, about lower natures with which lower reason is concerned; otherwise, Physics and Metaphysics would not be sciences. In the same way, higher reason also can in some way turn its attention to human acts, which depend on free will, and so are contingent; otherwise, sin, which occurs in such matters, would not be attributed to higher reason. Thus, higher reason is not completely distinct from the reasoning or conjectural part.

But the scientific part and the reasoning part are different powers because they are distinguished in relation to the nature of the intelligible object. For, since the act of any power does not extend beyond the scope of its object, every activity that cannot be reduced to the same formality of its object must belong to another power, which has another characteristic object. Now, the object of understanding is “something” (quid) as is said in The Soul. For this reason, the activity of understanding extends as far as the scope of the quiddity (quod quid est) of this “something” can extend. It is through this action that one at first knows principles themselves immediately, and from knowledge of these principles, by reasoning further, one arrives at knowledge of conclusions. This power, which is naturally ordained to analyze these conclusions into the quiddity (quod quid est), the Philosopher calls scientific.

However, there are some things in which it is impossible to perform such an analysis and to arrive at the quiddity, because of the uncertainty of their existence. This is the case with contingent things, in so far as they are contingent. Hence, these are not known through their quiddity, which is the proper object of understanding, but in another way, namely, through a kind of conjecture about those things concerning which we cannot have certitude. For this, then, a different power is needed. And, since this faculty cannot bring the inquiry of reason to its term, as it were, to rest, but stays with the investigation, as it were, in motion, and attains no more than opinion about the objects of its inquiry, this power is, therefore, called the reasoning or the conjectural power from the term of its activity. But higher and lower reason are distinguished according to natures themselves and, therefore, are not different powers as the scientific and the conjectural are.

4. The objects of the scientific and the reasoning parts are generically different by reason of the proper class of objects of knowledge, since they are known according to different intelligible characters. But eternal and temporal things differ in natural genus and not in their character of object of knowledge, according to which we must look for likeness between faculty and object.

5. Truth, which is the object of contemplation, and goodness, which is the object of activity, belong to different faculties, the understanding and the will. But higher and lower reason are not distinguished in this way, for both can be speculative and active, although by reason of different things, as has been shown above. Consequently, the conclusion does not follow.

6. Nothing prevents that which contains many things from being one with something else which contains many things if both contain the same things. Thus, this heap and this collection of stones are one and the same thing. In this way, higher and lower reason are the same faculty, although both in a sense contain several powers, since both contain the same powers. Moreover, higher reason is not said to include several powers in the sense that the power of reason itself is divided into different powers, but in so far as the will is included in the understanding. This does not mean that the will and the understanding are one faculty, but that the will is set in motion by the perception of the understanding.

7. Even in the sensitive part there is one power which has different functions, as the imagination, whose function it is to retain those things which have been received from the senses and represent them again to understanding. Accordingly, since the more immaterial a power is, the more things it can extend to, there is nothing to prevent one and the same power from having diverse functions in the intellective part, but not in the sensitive part.

8. Although the eternal and temporal are not reduced to the same proximate principle, knowledge of the eternal and of the temporal are reduced to the same principle since both are grasped according to one character of immateriality by one who understands.

9. According to Augustine, as man and woman, between whom there was the carnal marriage bond, belonged to human nature and the serpent did not, so lower reason, as woman, belongs to the nature of higher reason, whereas sensuality, as the serpent, does not.

10. Since sin is an act, properly speaking, it does not belong to either higher or lower reason, but to man according to the former or latter. And, if one power is related to different things, there is nothing inconsistent in having sin according to one relation and not according to the other. Thus, although several habits are in one power, it happens that one sins according to the act of one habit and not according to the act of another, for example, if the same man is grammarian and geometer, and he makes a statement containing truth about lines and also a solecism.

11. When a perfection brings the perfectible thing to completion according to its full capacity, it is impossible for one perfectible thing to have several perfections; in the same order. Therefore, matter cannot receive perfection from two subs ‘ tantial forms at the same time, because one matter has a capacity for only one substantial nature. However, the case is different with accidental forms, which do not give perfection to their objects according to their full potency. Consequently, it is possible for one perfectible thing to have many accidents. Therefore, there can be many habits of one power, since habitss are accidental perfections of powers, for they are superadded to the nature of the complete power.

12. As Avicenna says, diversity of act sometimes indicates diversity of powers and sometimes does not. For there can be diversity in the acts of the soul in five ways. In one, it is according to strength and weakness, as to conjecture and to believe. In the second, it is according to swiftness and slowness, as to run and to be put in motion. In the third, it is according to habit and privation, as to be at rest and to be moved. In the fourth, it is according to relation to opposites of the same genus, as to sense white and to sense black. It is in the fifth when the acts belong to different genera, as to perceive and to move, or to sense sound and to sense color.

Accordingly, diversity of the first and second type does not manifest diversity of power, for it thus would be necessary to have as many distinct powers of soul as there are grades of strength or weakness and swiftness or slowness in acts. Similarly, diversity of the third and fourth type does not indicate diversity of power, since it belongs to the same power to occupy itself with both opposites. Hence, only diversity of the fifth type manifests diversity of power, so that we say that acts are generically different which do not agree in the character of their object. The diversity of acts of higher and lower reason does not display diversity of power in this way, as is clear from what has been said.

13. Agent and possible intellect differ more than higher and lower reason, since agennand possible intellect refer to objects formally different, alth ‘ ough not materially different. For they refer to a different character of object, although both can be found in the same intelligible thing. For one and the same thing can first be intelligible in potency and then intelligible in act. But higher and lower reason refer to objects materially different, but not formally different. For they refer to different natures according to one character of object, as is clear from what has been said. But formal diversity is greater than material diversity. Therefore, the conclusion does not follow.

14. Lower reason is said to be drawn from higher reason because of the things which lower reason perceives, for these are drawn from those which higher reason perceives. For lower natures are drawn from higher natures. Consequently, nothing prevents higher and lower reason from being the same power. Similarly, we see that it belongs to the same power to study the principles of a subalternating science and the principles of a subalternate science, although the latter are drawn from the former.

15. Higher reason is said to move lower reason to this extent, that lower natures must be ruled according to higher natures, just as a subalternate science is ruled by the subalternating science.


Q. 15: Higher and Lower Reason


In the third article we ask:

Can sin exist in higher or lower reason?

[Parallel readings: II Sent., 24, 3, 1; S.T., I-II, 15, 4; 74, 7.]


It seems that it cannot, for

1. The Philosopher says: “The understanding is always correct.”, But reason is the same power as understanding, as was shown earlier. Therefore, reason is always correct. Therefore, there is no sin in it.

2. If anything that is receptive of some perfection is subject to defect, only, the defect which is opposite to the perfection can exist in it, since the same thing is receptive of contraries. But, according to Augustine, wisdom is the proper perfection of higher reason, and science is the proper perfection of lower reason. Therefore, stupidity and ignorance can be the only sins in higher or lower reason.

3. According to Augustine all sin is in the will. But reason is a different power from the will. Therefore, sin is not in reason.

4. Nothing is receptive of its opposite, for opposites cannot exist together. But every sin of man is contrary to reason, for the evil of man is to be contrary to reason, as Dionysius says. Therefore, sin cannot exist in reason.

5. A sin which is committed in regard to a certain subject matter cannot be attributed to the power which does not extend to that matter. But higher reason has eternal things and not delights of the flesh for its subject matter. Therefore, sins concerning pleasures of the flesh ought not in any way be attributed to higher reason, even though Augustine says that consent to an act is attributed to higher reason.

6. Augustine says that it is higher reason which contemplates higher things and clings to them, namely, through love. But sin does not restilt from this. Therefore, sin cannot exist in higher reason.

7. The stronger is not overcome by the weaker. But reason is the strongest of the powers which we have within us. Therefore, it cannot be overcome by concupiscence or anger or something else of that sort. Therefore, sin cannot exist in it.

To the Contrary

1. Merit and demerit belong to the same thing. But merit resides in the act of reason. Therefore, so does demerit.

2. According to the Philosopher” sin comes not only from passion, but also from choice. But choice consists in an act of reason, since it follows deliberation, as is said in the Ethics. Therefore, there is sin in reason.

3. Through reason we are directed in speculative and in practical matters. But in speculative matters there is sin of reason, as when one is guilty of paralogism in his reasoning. Therefore, in practical matters, also, there is sin in reason.


According to Augustine, sin is sometimes in higher reason and sometimes in lower reason. To understand this we must first know two things: which act can be attributed to reason; also, which can be attributed to higher, and which to lower, reason.

Accordingly, we must bear in mind that, just as the apprehensive part is twofold, namely, the lower, which is the sensitive, and the higher, which is the intellective or reasoning part, so the appetitive part, also, is twofold, namely, the lower, which is called sense appetite and is divided into concupiscent and irascible, and the higher, which is called will. These two appetitive parts relate to the corresponding apprehensive parts similarly in some respects and differently in others.

They relate similarly in this, that there can be no movement in either appetite unless some apprehension precedes. For that which is desirable moves the higher or lower appetite only when perceived by understanding or imagination or sense. Because of this, not only appetite, but also understanding, imagination, and sense, are called movers.

They relate differently in this, that there is a natural inclination in the lower appetite, by which it is in a way naturally forced to tend toward that which is desirable. But the higher appetite is not determined to one thing, since the higher appetite is free, whereas the lower is not. For this reason, movement of the lower appetite is not attributed to the apprehensive power, because the cause of that movement does not come from perception, but from an inclination of the appetite.

Movement of the higher appetite, however, is attributed to its apprehensive faculty, reason, because the inclination of the higher appetite toward this or that is caused by a judgment of reason. Consequently, we divide the sources of movement into rational, irascible, and concupiscent. In the higher part we use the names which belong to perception and in the lower the names which belong to appetite.

Therefore, it is clear that an action is attributed to reason in two ways. According to one way, it is attributed to it because it belongs to it directly, inasmuch as it is elicited by reason itself, for instance, the making of a comparison about objects of activity or of knowledge. In the other way, it is attributed to it because it belongs to it mediately through the will, since the will is set in motion through its judgment. Furthermore, just as a movement of appetite which follows a judgment of reason is attributed to reason, so a movement of appetite which follows deliberation of higher reason is attributed to higher reason. This happens when one bases his deliberation about practical matters on the fact that something is acceptable to God, or prescribed by divine law, or acts in some similar way. However, the movement of appetite will belong to lower reason when it follows a judgment of lower reason, as when one decides about practical matters on the basis of lower causes, as, for instance, considering the depravity of the act, the dignity of reason, the enmity of men, or something of this sort.

These two types of consideration are interrelated. For, according to the Philosopher, end has the character of principle in objects of activity. But in speculative sciences the judgment of reason reaches its perfection only when conclusions are analyzed into first principles. Hence, even in objects of activity the judgment of reason is brought to perfection only when there is reference to the last end. For only then will reason give the final decision on activity. And this decision is consent to the deed. Consequently, consent to the act is attributed to higher reason, which looks to the last end. But pleasure, whether it is complacency or consent in pleasure, is attributed to lower reason by Augustine.

Therefore, when one sins by giving consent to an evil act, the sin is in higher reason, but when one sins through pleasure alone with some deliberation, the sin is said to be in lower reason because the disposition of these lower things rests directly with it. Thus, sin is said to exist in higher or lower reason, in so far as the movements of appetite are attributed to reason. But, if we consider the proper act of reason, we say that sin is in the higher or lower reason when higher or lower reason is deceived in its proper act of comparison.

Answers to Difficulties

1. According to the Philosopher, just as sense is never deceived in its proper sensible objects, but can be deceived concerning common and accidental sensibles, so understanding is never deceived about its proper object, quiddity, except perhaps accidentally, nor about first principles, which are known as soon as the terms are known, but is deceived in comparing and applying common principles to particular conclusions. Thus it comes about that reason loses its correctness and sin exists in it.

2. Stupidity and ignorance are directly opposed to wisdom and science, as such, but in a certain sense all other sins are indirectly opposed to them, in so far as the rule of wisdom and science, which is required in activity, is perverted through sin. For this reason, every evil man is called one who does not know.

3 Sin is said to be in the will not as in a subject but as in a cause, for the thing must be voluntary to be a sin. But that which is caused by the will is also attributed to reason, for the reason mentioned above.

4. Man’s sin is said to be against reason in so far as it is against right reason, in which there can be no sin.

5. Higher reason is led directly to eternal essences as to its proper objects. But from them it is in some measure diverted to temporal and perishable things, inasmuch as it judges of these temporal things through the eternal essences. Thus, when its judgment about some matter is turned from its proper course, that is ascribed to higher reason.

6. Although higher reason is ordained to this, that it cling to eternal things, it does not always cling to them. Thus, there can be sin in it.

7. Socrates used a similar reasoning when he wanted to show that one who has certain knowledge does not sin, for, since certain knowledge is more powerful than passion, it is not overcome by it. In answer to this the Philosopher distinguishes certain knowledge into universal and particular, habitual and actual. And he makes a distinction in habitual certain knowledge on this basis, that a habit can be unhindered or repressed, as happens with those who are intoxicated. Accordingly, one who has universal knowledge in act may in a particular case with which a work is concerned have it only in a habit which is repressed through concupiscence or some other passion. As a result, the judgment of reason in the particular case cannot be informed according to the certain universal knowledge, and so it happens that reason errs in its choice. By reason of such an error of choice every evil man is one who does not know, however much certain knowledge in general he may have. In this way, also, reason is led to sin, inasmuch as it is repressed through concupiscence.


Q. 15: Higher and Lower Reason


In the fourth article we ask:

Is deliberate pleasure in bad thoughts (delectatio morosa),which exists in the lower part of reason through consent to the pleasure but without consent to the deed, a mortal sin?

[Parallel readings: II Sent., 24,3, 1, & 4; Quodl., XII, 22,33; S.T., I-II, 74, 6 & 8; 88, 5, ad 2.]


It seems that it is not, for

1. As Augustine says, striking the breast and [saying] the Our Father are the remedies given for venial sins. But consent to pleasure without consent to the deed is numbered among the sins for which striking the breast and [saying] the Our Father are accepted as a remedy. For Augustine says: “Now, when the mind takes pleasure in illicit things in thought alone, not, indeed, seeing them as something to be done, but still holding and gladly desiring these things which should be rejected as soon as they reach the soul, this should be considered to be a sin, but far less a sin than if it decided to carry it out in deed. Therefore, pardon should be sought for such thoughts, too, and we should strike our breasts and say: ‘Forgive us our trespasses.” Therefore, the above-mentioned consent in pleasure is not a mortal sin.

2. Consent to a venial sin is venial, as consent to a mortal sin is mortal. But pleasure is a venial sin. Therefore, consent to it is venial.

3. In the act of fornication we find two things for which it can be judged evil: the vehemence of the pleasure, which engulfs reason, and the harm coming from the act, namely, the uncertain condition of the children and other things of this sort which would result unless marital relations were regulated by law. But it cannot be said that fornication is a mortal sin by reason of the pleasure, for that intensity of pleasure exists in the marital act [in marriage], which is not a sin. Therefore, it is a mortal sin only because of the harm which comes from the act. So, one who consents to the pleasure of fornication, but not to the act, does not approach fornication under the aspect in which it is a mortal sin. Therefore, he does not seem to sin mortally.

4. Homicide is not less a sin than fornication. But one who thinks about homicide and takes pleasure and consents to the pleasure does not sin mortally. Otherwise, all who enjoyed hearing histories of wars, and consented to this pleasure, would sin mortally. But this does not seem probable. Therefore, consent to the pleasure of fornication is not a mortal sin.

5. Since venial and mortal sin are almost an infinite distance apart, which is seen from the distance between the punishment, a venial sin cannot become mortal. But the pleasure which consists in thought alone before consent is venial. Therefore, it cannot become mortal when the consent is added.

6. The essence of mortal sin consists in turning away from God. But to turn away from God belongs not to lower reason, but to higher reason, to which, also, it belongs to turn to God. For opposites belong to the same faculty. Therefore, mortal sin cannot exist in lower reason, and so the consent to pleasure which is ascribed to lower reason by Augustine is not a mortal sin.

7. As Augustine says: “If our desire is moved, it is like a woman being persuaded, but, finally, reason manfully curbs and represses our aroused desire. When this happens, we do not fall into sin.14From this, it seems, we perceive that in the spiritual marriage deep within us there is not sin if the woman sins, and the man does not. But when there is consent to pleasure and not to act, the woman sins, and not the man, as Augustine says. Therefore, consent to the pleasure is not a mortal sin.

8. According to the Philosopher, pleasure in good and evil follows the activity by which it is caused. But the exterior act of fornication, which consists in bodily movement, is different from the interior act, namely, the thought. Therefore, pleasure which follows the interior act will be different from that which follows the external act. But the interior act is not of its nature a mortal sin, as the external act is. Therefore, the interior pleasure is not classified as a mortal sin; hence, consent to such pleasure does not seem to be a mortal sin.

9. Only that seems to be a mortal sin which is forbidden by divine law, as is clear from the definition of sin given by Augustine: “Sin is word or deed or desire against the law of God.” But there is no law forbidding consent to pleasure. Therefore, it is not a mortal sin.

10. It seems that we should pass the same judgment on interpretative consent and on express consent. But interpretative consent does not seem to be mortal sin because sin is carried over to another faculty only through an act of that faculty. In interpretative consent, however, there is not any act of reason, which is said to consent, but only negligence in repressing illicit movements. Therefore, interpretative consent to pleasure is not a mortal sin, and express consent is, likewise, not a mortal sin.

11. As has been said, an act is a mortal sin because it is against a divine precept. Otherwise, God would not be despised in the transgression of the precept, and thus the mind of the sinner would not be turned away from God. Lower reason, however, does not take the norm of the divine precept into consideration. For this is the task of higher reason, which considers eternal norms. Therefore, there can be no mortal sin in lower reason; hence, consent mentioned above is not a mortal sin.

12. Since there are two elements in sin, turning toward and turning away, the turning away follows the turning toward. For, by the very fact one turns toward one contrary, he turns away from the other. But he who consents to the pleasure and not to the act does not fully turn to changeable good, since completeness is in the act. Therefore, in this there is not complete turning away; hence, no mortal sin.

13. As the Gloss says: “God is more inclined to be merciful than to punish.” But, if one took pleasure in meditating on divine commands and consented to such pleasure, he would not merit, as long as he did not propose to fulfill the divine commands in deed. Therefore, neither will one merit punishment if he consents to the pleasure of sin, provided that he does not decide to fulfill it in deed. Accordingly, lie does not seem to sin mortally.

14. The lower power of reason is compared to woman. But woman is not mistress of her will, for, as the Apostle says (1 Cor 7:4): she “does not have power over her body.” Therefore, neither is the lower part of reason master of its will; hence, it cannot sin.

To the Contrary

1. No one is damned except for mortal sin. But man will be damned for consent to pleasure. Hence, Augustine says: “The whole man will be damned, unless these things which are perceived to be sins only of thought, and which exist without the will to do them, but still with the will to delight the mind with them, are remitted through the grace of the Mediator.” Therefore, consent to pleasure is a mortal sin.

2. Pleasure in an activity and the activity itself are reduced to the same genus of sin, just as the activity of a virtue and pleasure in it are reduced to the same virtue. For it belongs to the just man to perform just deeds and to take pleasure in them, as is clear in the Ethics. But the act of fornication is classified as a mortal sin. Therefore, the pleasure in the thought of fornication is, too. Therefore, consent to the pleasure will be a mortal sin.

3. If there could not be mortal sin in lower reason, gentiles, who consider only the lower norms of action, would not sin mortally by fornicating or doing something of the sort. This is obviously false. Therefore, there can be mortal sin in lower reason.


The question whether deliberate pleasure in bad thoughts is a mortal sin and the question about consent to pleasure is the same. For there can be no doubt whether deliberate pleasure in bad thoughts is a sin, if it is called such (morosa) from duration (mora) of time. For it is certain that mere length of time cannot give an act the character of mortal sin, unless something else intervenes, since length of time is not a circumstance aggravating to infinity. But what is doubtful seems to be this: whether the pleasure which is called such because of the superadded consent of reason is a mortal sin. There have been different opinions about this.

For some have said that it is not a mortal sin, but venial. This opinion seems to be opposed to the words of Augustine, who threatens man with damnation because of such consent, as is clear from the passage cited. Furthermore, the almost universal opinion of moderns contradicts this [first] position, which seems, also, to tend toward danger for souls, since from consent in such pleasure a man can very readily fall into sin.

Hence, it seems that we must accept the second opinion, which makes such consent a mortal sin. The truth of this position can be seen from the following. For we must bear in mind that, just as sensible pleasure follows on the external act of fornication, so interior pleasure follows on the act of thinking. But a double pleasure follows on thought. One of these follows from the thought and the other from the thing thought of. For at times we take pleasure in thought because of the thought itself, from which we get actual knowledge of certain things, although the things displease us. Thus, a just man thinks about sins when he discusses or argues about them, and takes pleasure in the truth of this thought. But the pleasure follows because of the things thought when the thing thought about itself stirs up and attracts the affections. In some acts, these two thoughts obviously differ and are clearly distinct. But their distinction is more obscure in thoughts about sins of the flesh, because, due to the weakened condition of the concupiscible part, when there is thought of such desirable objects, there immediately follows in the concupiscible part a movement which is caused by these objects.

Therefore, the pleasure which follows thought because of the thought is ascribed to an altogether different genus than the pleasure of the exterior act. Consequently, when any such pleasure follows the thought of evil things, it is either no sin at all, but a praiseworthy pleasure, as when one takes delight in the knowledge of the truth; or, if there is some lack of moderation, it is classed under the sin of curiosity.

But the pleasure which follows thought because of the thing thought about belongs to the same class as the pleasure of the external act. For, as is said in the Metaphysics, pleasure consists essentially in the act, but the hope and memory are pleasurable because of the act. From this it is clear that such pleasure is inordinate in its genus by reason of the same disorder which makes external pleasure inordinate.

Accordingly, if the external pleasure is conceded to be mortally sinful, then the interior pleasure, considered in itself and independently, belongs to the genus of mortal sin. Moreover, mortal sin results whenever reason gives itself over to mortal sin by approving of it. For the uprightness of justice is banished from reason when it is made subject to evil by approving of it. And reason makes itself subject to this disordered pleasure when it consents to it. This is the first subjection by which it enslaves itself. Sometimes, there follows on this subjection the choice of the disordered act itself, in order to attain this pleasure more perfectly. And, the more it seeks for further disorders to obtain pleasure, the more it advances in sin. Yet the consent by which it accepted the pleasure will be the first root of that whole progression. Thus, mortal sin begins there.

Consequently, we concede without reserve that consent in the pleasure of fornication or of any other mortal sin is a mortal sin. From this it also follows that whatever a man does because of consent to such pleasure with a view to fostering or holding it, such as shameful touches, or lustful kisses, or things such as these, the whole thing is a mortal sin.

Answers to Difficulties

1. As Augustine says, [saying] the Our Father and [doing] other works of this sort have value not only to wipe out venial sins, but also for the remission of mortal sins, although they are not sufficient for the remission of mortal sins as they are for the remission of venial sins.

2. The pleasure that follows the pleasure in fornication because of the thing thought about is of its nature mortal, but it can be venial accidentally, in so far as it precedes deliberate assent which gives mortal sin its complete character. Without this, if the body were defiled by violence, there would not be mortal sin, for, as Lucy says, the body cannot be defiled with the defilement of sin without the consent of the mind. Therefore, when consent comes, the above-mentioned accident is withdrawn and there is mortal sin, as would happen in a woman who, if she gave consent, would be corrupted through violence.

3. The whole disorder of fornication, from whatever source it arises, flows over into the pleasure which it causes. Hence, one who approves pleasure of this sort sins mortally.

4. If one took pleasure in the thought of murder because of the thing thought about, this would be only by reason of an inclination which he had toward murder; hence, he would sin mortally. However, if one took pleasure in such thought because of knowledge of the things about which he is thinking, or for some other reason of this sort, it would not always be a mortal sin. It would, rather, be classed under some other genus of sin than murder, such as curiosity or something else of this sort.

5. The pleasure which was venial will never, as numerically the same, become mortal, but the act of consent added to it will be a mortal sin.

6. Although higher reason alone is of itself directed to God, lower reason to some degree shares in this conversion, in so far as it is ruled by higher reason. Similarly, the concupiscent and irascible are said to share in reason to some degree in so far as they obey reason. Thus, the turning away [from God] in mortal sin can belong to lower reason.

7. In Against the Manichaeans, Augustine does not explain those three things as he does in The Trinity. In the latter, he attributes serpent to sensuality, woman to lower reason, and man to higher reason; whereas, in the former he attributes serpent to sense, woman to concupiscence or sensuality, and man to reason. Therefore, it is clear that the conclusion does not follow.

8. The internal act, that is to say, thought, has pleasure of a kind different from the pleasure of the external act. And this follows thought for its own sake. But the pleasure which follows thought because of the act thought about is put in the same class [as the act] because no one takes pleasure in something unless he is attached to it and perceives it as agreeable. Consequently, one who consents to interior pleasure also approves the exterior pleasure and wants to enjoy it, at least by thinking about it.

9. Consent to pleasure is forbidden by the precept: “Thou shall not covet...” (Exod. 20:17; Dent. 5:21). For it is not without cause that different precepts are given in the law for the external act and the internal desire. Nevertheless, even if it were not forbidden in any special commandment, all the consequences of fornication which concern the same object would be forbidden by the very fact that fornication is forbidden.

10. Before reason considers its own pleasure or harm, it does not have interpretative consent, even though it does not resist. But, when it has considered the rising pleasure and the harm that will follow, it seems to consent, as a man seems to consent, unless he openly resists when.he perceives that he will be completely drawn to sin by pleasure of this sort, and will fall headlong. Then the sin is attributed to reason because of its act, since to act and not to act when one should are reduced to [one] genus, inasmuch as sin of omission is reduced to sin of act.

11. The force of a commandment of God reaches lower reason inasmuch as it shares the rule of higher reason, as has been said.

12. The conversion by which one turns after deliberation to something which is of its nature evil is sufficient for the character of mortal sin, although another complete act can be added to this one.

13. As Dionysius says: “Good is caused by one whole and complete cause, but evil by individual defects.” Thus, more things are required for something to be a meritorious good than for it to be a blameworthy evil, although God is more inclined to reward good deeds than to punish evil ones. Consequently, consent to pleasure without consent to the deed is not enough for merit, but, when there is question of evil, it is enough for blame.

14. By right a woman ought not to will anything contrary to the just appointment of her husband, but, as a matter of fact, sometimes one can and does will the opposite. Thus it is with lower reason.

Answers to Contrary Difficulties

We concede the arguments to the contrary, although the last concludes falsely. For it proceeds as though a gentile could not sin according to higher reason. And this is false, for there is no one who does not judge that something is the end of human life. And, when he uses that as a basis of his deliberation, he is using higher reason.


Q. 15: Higher and Lower Reason


In the fifth article we ask:

Can venial sin exist in higher reason?

[Parallel readings: Il Sent., 24,3,5; S.T., I-II, 74, 9-10; Q.D. de malo, 7, 5.]


It seems that it cannot, for

1. It belongs to higher reason to cling to the eternal norms of conduct. Therefore, sin can be in it only in so far as it turns away from these eternal norms. But to turn away from them is a mortal sin. Therefore, there can be only mortal sin in higher reason.

2. Through contempt venial sin becomes mortal. But there seems to be contempt when one considers something to be evil and to be punished by God and, nevertheless, consents to commit it. Therefore, it seems that there is a mortal sin whenever one consents to the act even of a venial sin after the consideration of higher reason.

3. There is something in the soul, sensuality, in which there can be only venial sin, and something in which there can be venial and mortal sin, namely, lower reason. Therefore it seems that there is also something in the soul in which there can be only mortal sin. But this is not synderesis, because in that there is no sin. Therefore, this description fits higher reason.

4. In angels and in man in the state of innocence there could not be venial sin, because venial sin arises from the weakening of the flesh, and this did not then exist. But higher reason is apart from the weakening of the flesh. Therefore, there can be no venial sin in it.

To the Contrary

1. Consent to the act of sin is not more serious than the act of sin itself. But consent to the act of venial sin belongs to higher reason. Therefore so does venial sin.

2. An unpremeditated movement of infidelity is a venial sin, and this takes place only in higher reason. Therefore, there is venial sin in it.


There can be venial and mortal sin in the higher part of reason. Nevertheless, there is some subject matter concerning which there can be only mortal sin in higher reason. This is plain in what follows. For higher reason has an act concerning some matter directly, that is, concerning eternal norms, and an act concerning some matter indirectly, that is, temporal norms, about which it judges according to eternal norms. With reference to its proper matter, eternal norms, it has a double act, one unpremeditated and one deliberate. But, since mortal sin is committed only after the act of deliberation, there can be venial sin in higher reason when there is an unpremeditated movement, and mortal when there is deliberate movement, as we see in the sin of infidelity. But it has only a deliberate act with reference to the matter of temporal things because it is directed to them only when it compares the eternal norms with them. Consequently, the act of higher reason will always be a mortal sin in this matter, if such matter is by nature a mortal sin. But, if it is by nature a venial sin, it will be venial, as is clear when one gives consent to an idle word.

Answers to Difficulties

1. Higher reason sins in this, that it turns away from eternal norms not only by acting against them, but by acting outside them, which is a venial sin.

2. Not every contempt makes a sin mortal, but contempt of God. And through this alone man is turned away from God. But, when one consents to a venial sin after any deliberation, no matter how much, he does not have contempt of God, unless, perhaps, he would judge that the sin is contrary to a divine commandment. Thus, the conclusion does not follow.

3. That there can be only venial sin in sensuality comes from its imperfection. But reason is a perfect power and, therefore, there can be sin in it according to every difference of sin. For its act can be complete in any genus. Hence, if it is by nature a venial sin, it is venial; if it is by nature a mortal sin, it is mortal.

4. Although higher reason is not directly connected with the flesh, the weakening of the flesh reaches it, inasmuch as higher powers receive something from the lower powers.