4-3
BOOK VIII
PRINCIPLES OF SENSIBLE SUBSTANCESLesson 1
Sensible substance is matter, form, composite.
1686. Having linked up the foregoing discussion with the one that is to come, the Philosopher begins here to treat of sensible substances by investigating their principles. This is divided into two parts. In the first (1686) he establishes what is true concerning matter and form, which are the principles of sensible substances. In the second (1755) he considers the way in which they are united to each other ("It seems that we must").
In regard to the first he does two things. First, he shows that matter and form are principles of sensible substances. Second (1705), he deals with those points which must be investigated about each of these principles ("And we must not").
In regard to the first he does two things. First, he shows that matter is a principle of sensible substances; and second (1691), that the same is true of form ("But since that which has the character of a subject").
In regard to the first he does three things. First he shows what matter is by distinguishing it from the other ways in which substance is considered. Hence he says that all sensible substances have matter; and the reason is that all are in motion, and motion does not exist without matter.
1687. But it must be noted that in one sense substance means (1) matter, and in another (2) form, and in still another (3) the thing composed of these.
For matter is called substance, not as though it were a being considered to have actual existence in itself, but as something capable of being actual (and this is said to be a particular thing).
And form, which is also termed the intelligible structure because the intelligible structure of the species is derived from it, is called substance (1) inasmuch as it is something actual, and (2) inasmuch as it is separable from matter in thought but not in reality.
And the thing composed of these is called substance inasmuch as it is something "separable in an absolute sense," i.e., capable of existing separately by itself in reality; and it alone is subject to generation and corruption. For form and matter are generated and corrupted only by reason of something else.
And although the composite is separable in an absolute sense, yet some of the other things which are called substances are separable in thought and some are not. For a form is separable in thought because it can be understood without understanding individuating sensible matter; but matter cannot be understood without understanding form, since it is apprehended only inasmuch as it is in potentiality to form.
Or the, statements can mean that "according to the intelligible structure of substances," i.e., of forms, some are separable in their intelligible structure, as the objects of mathematics, and some are not, as natural forms.
Or again it may mean that there are certain separate forms existing without matter, about which he will establish the truth later on (2447-2454).
1688. Second, he says that in sensible substances we must posit matter as substance and subject. For in every change between contraries, there must be a subject common to the termini of the change. For example, in change of place there is a common subject which is now here and afterwards somewhere else; and in growth there is a common subject which now has so much quantity and afterwards is smaller (if the change is decrease) or greater (if it is increase). And in alteration there is a common subject which is now healthy and afterwards diseased. Hence, since there is substantial change, that is, generation and corruption, there must be a common subject which underlies the opposite changes of generation and corruption. And this is the subject for the termini that have been given, i.e., form and privation, so that sometimes this subject is actual by reason of a form, and sometimes it is the subject of the privation of that form.
Lesson 2
1697. For just as in the genus of substance the difference, which is predicated of the genus and qualifies it in order to constitute a species, is related to the genus as actuality or form, so also is this true in other definitions.
(~) For we must not understand that difference is form or that genus is matter, since genus and difference are predicated of the species but matter and form are not predicated of the composite. (+) But we speak in this manner because a thing's genus is derived from its material principle, and its difference from its formal principle.
The genus of man, for example, is animal, because it signifies something having a sensory nature, which is related as matter to intellectual nature from which rational, the difference of man, is taken. But rational signifies something having an intellectual nature.
It is for this reason that a genus contains its differences potentially, and that genus and difference are proportionate to matter and form, as Porphyry says . And for this reason too it is said here that "actuality," i.e., difference, is predicated "of matter," i.e., of the genus; and the same thing occurs in other genera.
Lesson 3
1708. Then the Philosopher shows the result to which the aforesaid search leads. He says that, while the question whether a specific name signifies the composite substance or only the form, (+) makes a difference in regard to something else, (~) it makes no difference to the investigation of sensible substance. For it is evident that a sensible substance is composed of matter and form.
1709. (+) Now to what kind of thing it makes a difference, whether to those in this state or in another, he makes clear next. For it is obvious that if there is something which is only form or actuality, its essence "consists of this," i.e., the thing and its essence will be identical, as a soul is identical with its essence, or is its own quiddity.
But if a thing is composed of matter and form, then in this case the thing itself and its essence will not be the same; for example, a man and the essence of a man are not the same, unless perhaps a man is said to be only a soul, as was held by those who say that specific names signify only the form. Thus it is evident that something does exist whose essence is the same as itself, namely, whatever is not composed of matter and form but is only a form.
1710. The reason for this position is that essence is what the definition signifies, and the definition signifies the nature of the species. But if there is something which is composed of matter and form, then in that thing there must be some other principle besides the nature of the species. For since matter is the principle of individuation, then in anything composed of matter and form there must be certain individuating principles distinct from the nature of the species. Hence such a thing is not just its own essence but is something in addition to this. But if such a thing exists which is only a form, it will have no individuating principles in addition to the nature of its species. For a form that exists of itself is individuated of itself. Therefore this thing is nothing else than its own essence.
1711. It is clear, then, that if the specific name signifies only the form, the essence of anything will be (+) the same as its being, as a man will be his essence, and a horse its essence, and so also will all other things of this kind.
But if specific names signify things composed of matter and form, then such things will (~) not be the same as their essence.
1727. He gives the fourth way in which forms are like numbers. He says that just as a number does not admit of (~) more or less, neither does substance in the sense of form, although perhaps substance in the sense of matter does admit of such difference. For just as the concept of number consists in some limit to which neither addition nor subtraction may be made, as has been pointed out (1723), so also does the concept of form.
But things admit of (+) more or less because of the fact that matter participates in a form in a more or less perfect way. Hence too whiteness does not differ in terms of more or less, but a white thing does.
Lesson 4
Matter
1743. He shows how matter is ascribed to accidents. He says that those things which exist by nature yet are not substances but accidents, (~) do not have a matter from which they come to be, but (+) they have a subject, which is the substance. Now a subject bears some likeness to matter inasmuch as it is receptive of an accident. But it differs from matter in this respect, that while matter has actual being only through form, a subject is not constituted in being by an accident.
1744. Therefore, if one asks what is the cause of an eclipse, one cannot give its (~) matter, but the moon is the (+) subject undergoing this modification.
And the efficient cause which extinguishes the light is the earth placed directly between the sun and the moon.
But perhaps it is impossible to give the final cause; for those things which pertain to defect do not exist because of some end but are rather a result of natural necessity or of the necessity of the efficient cause. However, he says "perhaps" because an investigation of the causes of particular events which take place in celestial movements is especially difficult.
And the formal cause of an eclipse is its definition. But this definition is not clear unless the [efficient] cause is given therein. Thus the definition of a lunar eclipse is the privation of light in the moon. But if one adds that this privation is caused by the earth being placed directly between the sun and the moon, this definition will contain the [efficient] cause.
Lesson 5
1760. Then he solves the above problem in regard to the objects of mathematics. He says that matter is of two kinds, sensible and intelligible.
Sensible matter is what pertains to the sensible qualities, hot and cold, rare and dense and the like; and with this matter natural bodies are concreted. Now the objects of mathematics abstract from this kind of matter.
But intelligible matter means what is understood without sensible qualities or differences, for example, what is continuous. And the objects of mathematics do not abstract from this kind of matter.
1761. Hence, whether in the case of sensible things or in that of the objects of mathematics, their definitions must always contain something as matter and something as form; for example, in the definition of a mathematical circle, a circle is a plane figure, plane is as matter and figure as form. For a mathematical definition and a natural definition are each one thing on the same grounds (even though there is no agent in the realm of mathematical entities as there is in the realm of natural entities), because in both cases one part of the definition is as matter and the other as form.
1762. He solves the above problem in regard to the things that are wholly separate from matter. He says that in the case of all those things which do not have intelligible matter, as the objects of mathematics have, or sensible matter, as natural bodies have, that is to say, in the case of the separate substances, each one of these is at once one thing [individuated by form].
For each of those things which have matter is not at once one thing, but they are one because unity comes to their matter. But if there is anything that is only a form, it is at once one thing, because it is impossible to posit in it anything prior in any order whatever that must await unity from a form.
1763. He gives this example: the ten categories do not derive being by adding something to being in the way that species are established by adding differences to genera, but each is itself a being. And since this is true, it is evident that being does not await something to be added to it so that it may become one of these, i.e., either a substance or quantity or quality; but each of these from the very beginning is at once either a substance or quantity or quality.
This is the reason why neither unity nor being is given as a genus in definitions, because unity and being would have to be related as matter to differences, through the addition of which being would become either substance or quality.
1764. Similarly, that which is wholly separate from matter and is its own essence, as was stated above (1708), is at once one thing, just as it is a being; for it contains no matter that awaits a form from which it will derive being and unity. In the case of such things, then, there is no cause that makes them one by means of motion.
However, some of them have a cause which supports their substances without their substances being moved [separate simple substances depend on God for existence], and not as in the case of things subject to generation, which come to be through motion. For each of them is at once a particular being and a one, but not so that being and unity are certain genera or that they exist as individuals apart from singular things, as the Platonists held.