Commentary Aristotle Physics
Second, at “now the subject” (190b23; [112]), he shows that the third principle is a per accidens principle of nature.
111. With reference to the first point, he uses the following argument (190b17). Those things from which natural things are and come to be per se, and not per accidens, are said to be the principles and causes of natural things.
Whatever comes to be exists and comes to be both from subject and from form. Therefore, the subject and the form are per se causes and principles of everything that comes to be according to nature.
He proves as follows that what comes to be according to nature comes to be from subject and form. Those things into which the definition of a thing is resolved are the components of that thing, because each thing is resolved into the things of which it is composed.
But the definition of that which comes to be according to nature is resolved into subject and form. For the definition of musical man is resolved into the definition of man and the definition of musical. For if anyone wishes to define musical man, he will have to give the definitions of man and musical. Therefore, that which comes to be according to nature both is and comes to be from subject and form.
And it must be noted that he intends here to inquire not only into the principles of the coming to be but also into the principles of the being.
Hence he says significantly that things primarily are or have come to be from these first principles. And, by first principles, he means per se and not per accidens principles. Therefore, the per se principles of everything that comes to be according to nature are subject and form.
112. Next, at “now, the subject” (190b23), he adds the third, per accidens principle. He says that, although the subject is one in number, it is nevertheless two in species and account, as was said above. For man and gold and any matter has some sort of number. This is a consideration of the subject itself, such as man or gold, which is something positive, and from which something comes to be per se and not per accidens. It is another thing, however, to consider that which happens to the subject, namely, contrariety and privation, such as to be unmusical and unshaped.
The third principle, then, is a species or form, as arrangement is the form of a house or musical is the form of a musical man, or as any of the other things that are predicated in this way. Therefore, the subject and the form are per se principles of that which comes to be according to nature, but privation or the contrary is a per accidens principle, insofar as it happens to the subject. In this way, we say that the builder is the per se active cause of the house, but the musician is a per accidens active cause of the house insofar as the builder also happens to be musical. Hence, the man is the per se cause as subject of musical man, but the non-musical is a per accidens cause and principle.
113. However, someone may object that privation does not belong to a subject while it is under some form, and thus privation is not a per accidens principle of being. Hence it must be said that matter is never without privation. For when matter has one form, it is in privation of some other form. And so, while it is coming to be that which it becomes (such as musical man), there is in the subject, which does not yet have the form, the privation of the musical itself. And so, the per accidens principle of a musical man, while he is coming to be musical, is the non-musical. For he is a non-musical man while he is coming to be musical. But when this latter form has already come to him, then there is joined to him the privation of the other form. And thus the privation of the opposite form is a per accidens principle of being.
It is clear, therefore, according to the opinion of Aristotle, that privation, which is set down as a per accidens principle of nature, is not a capacity for a form, nor an inchoate form, nor some imperfect active principle, as some say. Rather, it is the very absence of form or the contrary of form that occurs in the subject.
114. Next, at “thus, there is one sense” (190b29), he resolves, in the light of the truth already determined, all the preceding difficulties. He concludes from the foregoing that, in a certain respect, it must be said that there are two principles—namely, the per se principles—and that in another respect there are three, if we accept along with the per se principles also the per accidens principle.
And, in a certain respect, the principles are contraries, if one takes the musical and the non-musical, the hot and the cold, or the harmonious and the inharmonious. Yet, in another respect, if they are taken without the subject, the principles are not contraries, for contraries cannot be acted upon by each other, unless it be held that some subject is supposed for the contraries by reason of which they are acted upon by one another. And thus he concludes that the principles are not more than the contraries, for there are only two per se principles.
But there are not just two principles, for one of them according to its being is other, for the subject according to account is two, as was said. And thus, there are three principles, because man and the non-musical, and bronze and the unshaped, differ according to account. Therefore, it is clear that the early opinions that argued for either part of the truth were in a certain respect true, but not altogether true.
115. Next, at “we have now stated” (191a3), he shows in what way two contraries are necessary and in what way they are not necessary. He says that, from what has been said, the number of natural generation’s principles is clear, and how it happens that there are this number.
For it was shown that it is necessary that two of the principles be contraries, of which one is a per se principle and the other a per accidens principle, and that something be the subject of the contraries, which is also a per se principle. But, in a certain respect, one of the contraries is not necessary for generation, for at times, it is sufficient if one of the contraries bring about the change by its absence and its presence.
116. As evidence of this we must note that, as will be said in book 5, there are three species of change: generation, corruption, and motion. The difference among these is as follows.
Motion is from one positive state to another positive state, as from white to black.
Generation, however, is from the negative to the positive, as from the non-white to the white, or from non-man to man.
Corruption, on the other hand, is from the positive to the negative, as from the white to the non-white, or from man to non-man.
Therefore, it is clear that, in motion, two contraries and one subject are required. But, in generation and corruption, there is required the presence of one contrary and its absence, which is privation.
Generation and corruption, however, are found in motion. For when something is moved from white to black, white is corrupted and black comes to be. Therefore, in every natural change, subject and form and privation are required.
However, the account of motion is not found in every generation and corruption, as is clear in the generation and corruption of substances. Hence subject and form and privation are found in every change, but not a subject and two contraries.
117. This opposition is also found in substances, which are the first genus, but the opposition of contrariety is not. For substantial forms are not contraries, even though differentiae in the genus of substance are contrary, insofar as one is received along with the privation of the other, as is clear in the animate and the inanimate.
118. Next, at “the underlying nature” (191a7), he clarifies the above-mentioned principles. He says that the nature that is first subject to change—prime matter—cannot be known through itself, since everything that is known is known through its form. Prime matter is, moreover, considered to be the subject of every form. But it is known by analogy, that is, according to proportion.
For we know that wood is other than the form of a bench and a bed, for sometimes it underlies the one form, but at other times it underlies the other. Therefore, when we see that air at times becomes water, it is necessary to say that there is something that sometimes exists under the form of air, and at other times under the form of water. And thus, this something is other than the form of water and other than the form of air, as wood is something other than the form of a bench and other than the form of a bed. This something, then, is related to these natural substances as bronze is related to the statue, and wood to the bed, and anything material and unformed to form. And this is called “prime matter.”
This, then, is one principle of nature. It is not one as the “this something”—that is, as some determinate individual, as though it had form and unity in act—but is rather called “being” and “one” insofar as it is in potency to form. The other principle, then, is the account or form, and the third is privation, which is contrary to the form. And how these principles are two and how they are three was explained above.
119. Next, at “briefly, we explained” (191a15), he summarizes what has been said and points out what remains to be said.
He says, therefore, that it was said first that the contraries are principles, and afterwards that something is subjected to them, and thus there are three principles. And, from what was said just now, it is clear what the difference is between the contraries: one of them is a per se principle, and the other a per accidens principle.
And then it was pointed out how the principles are related to each other, since the subject and the contrary are one in number yet two in account.
Then it was pointed out what the subject is insofar as this could be made clear. But it has not yet been decided which is more substance, form or matter, for this will be explained at the beginning of book 2.
But it has been explained that the principles are three in number, how they are principles, and in what way.
And he finally draws the conclusion he principally intended, namely, that it is clear how many principles there are and what they are.