Disputationes metaphysicae

1. There is another principal opinion on this matter, that the internal principle of individuation is the substantial form. This is wont to be attributed to Durandus, In II, dist. 3, q. 2, who does not altogether affirm it, as I shall say afterwards; but Averroes seems to have taught it, De Anima I, c. 7, and Book II, at the beginning, and comms. 7, 8, 9 and 60, and Physics III, comm. 60, and Book IV, comm. 38; Avicenna too is cited, Naturalia VI, part I, saying that the form gives numerical unity to the subject; Zimara holds it, Theorem 97; and Sebastian, bishop of Osma, De Anima II, c. 1. And Aristotle favours it in the same place, when he says that the form is what constitutes a this something. And from this word of Aristotle the chief foundation of this opinion is to be taken; for the principle of individuation must be that which intrinsically constitutes this substance and is most proper to it; therefore by reason of the first property it must be something substantial; for accidents, as has often been said, neither constitute substance nor this substance; for this substance, even as it is this, is being per se and substantial. But by reason of the other property this principle cannot be matter, but form, because this matter is not most proper to this individual, since it can be under other forms; therefore form is the principle of individuation.

2. Whence I argue, secondly, that the principle of unity and of entity is the same; on account of which St. Thomas said, sole question De Anima, a. 1, ad 2, that each thing has being and individuation according to the same. But each thing properly has being from its form; therefore also individual unity. The major is evident, because unity is an attribute following upon entity and adds to it only a negation; therefore it cannot have another positive and real principle except that which is the principle of the entity itself.

3. But someone will object against this opinion and reason that, although it rightly proves that form contributes to unity, it does not prove that it alone is the principle of individuation; for matter too is an intrinsic principle constituting the entity of the thing, and therefore it too will be a principle of individuation, if not alone, at least with form. It could be answered according to the opinion of Durandus, In IV, dist. 44, q. 1, that form has the power of individuating not only the composite but also matter itself, because form gives being not only to the composite but also to matter; whence it comes about (he says) that by the very fact that matter is joined to the same form in number, it itself is the same in number. But this opinion of Durandus is false, and is deservedly rejected by the other theologians, as I showed in tom. 2 of the Third Part, disp. XLIV, sect. 2. For one and the same matter in number which was in what was corrupted remains in what is generated; otherwise the subject from which generation comes about would not be the same in number. Likewise, because it is impossible either that a thing which before was distinct in number from another should afterwards become that other, or the same in number with it indivisibly, or that a thing which was one in number should afterwards according to its whole self become another distinct in number; therefore the matter which under the form of food is one in number cannot become another in number through beginning to be under the form of the soul; and the matters of Peter and Paul, which are distinct in number, will not become one in number, even if they are successively under the form of Peter and of Paul. Finally, otherwise the same matter in number once annihilated would be restored through the mere union of another matter to the same form; and we are speaking of true unity according to real and physical entity, and not only according to appearance or the vulgar manner of speaking, in which way a thing which is in continual flux and is changed only little by little is wont to be called one; for in this way, even if the change takes place in the form, such a unity can be preserved, as is evident in a river, or in a tree or a brute.

4. The answer, then, is otherwise: that it is indeed true that the adequate intrinsic cause of the individual unity of material substance is form and matter, as the argument concludes; yet, if these two are compared among themselves, the chief cause of this unity is the form, and in this sense it is specially attributed to it that it is the principle of individuation. Just as matter too is necessary for the specific notion or unity; for the notion of man or of humanity as such cannot be constituted without matter, and the same holds of the generic notion of animal, living thing, etc.; and nevertheless the specific notion is absolutely said to be taken from the form, because it gives the ultimate completion and only presupposes matter as something potential and indifferent; by the same reason, then, it will be called the principle of individuation, because it gives the ultimate substantial completion to the individual, although it presupposes matter as of itself potential and indifferent; on account of which Aristotle said, above, and Physics I, c. 7, text 69, that the form constitutes a this something. And since, as we were saying above, a thing is distinguished through the same thing through which it is constituted, the same form which constitutes this something distinguishes it from others, since it is act which distinguishes, Metaphysics VII, c. 13, text 49; therefore it is the form which completes the notion of the individual. And the common mode of conceiving and speaking confirms this; for if to the soul of Peter, for example, there is united a body consisting of matter distinct from the body which it had before, although that composite is not in every respect the same as it was before, nevertheless, simply speaking, that individual is called the same by reason of the same soul; but conversely, if to a body consisting of the same matter a soul distinct in number is united, it is simply not judged the same individual, but a distinct one; it is therefore a sign that individuation is taken chiefly from the form.

5. But it is further objected against this opinion and the reason given that, although form as such gives specific being, it does not give individual and numerical being except as it is this; therefore not form as such, but that whence the form itself has it that it is this, is the principle of individuation; but it is this by reason of matter; therefore matter rather is the first root of individuation. The minor is proved, first, because form is not this by itself; otherwise the same could be said of any entity whatever, nor would it be necessary to seek another principle of individuation; therefore it is this through matter, for no other root can be thought out. Secondly, because form has its whole being in order to matter; therefore also its individuation; therefore matter is the principle of the individuation of form, and consequently of the whole composite. Thirdly, because forms are multiplied in number in so far as they are received in diverse matters, and therefore separated forms are not multiplied in number, because they are not received in matter; therefore they are individuated also through order to matter; the ultimate resolution of this individuation, therefore, is made to matter; for this form is this because it is received in such matter; therefore the first root of individuation is matter.

6. These objections are the foundations of the opinion treated in the preceding section, which rather declare and confirm this opinion which we are now treating. For almost all of them can be retorted and made of matter itself. I concede, then, that form is not the principle of the individuation of the composite according to its specific notion, as is self-evident, but in so far as it is this; but this very thing must be said of matter, because matter too has a specific and common notion, according to which it is not sufficient to constitute the individual; therefore, if it constitutes it, it does so in so far as it is this. I shall ask again, then, whence it has it that it is this. Some answer, because God willed to create this rather than another; but this is beside the point, for we are not here inquiring into the extrinsic principle of individuation, but the intrinsic one; otherwise someone could also say that this soul is this because God willed to infuse it rather than another; or that this form is this because God determined his concurrence to it, as is very probable, as we shall say in the following section. Others answer that this matter is this by reason of this quantity. But this both is false and does not remove the difficulty. The first is evident from what has been said above, because, since this matter is simply supposed to this quantity, it cannot be individuated through it. Likewise, because the reasons made above prove universally that nothing substantial can be individuated through a superadded accident; for this matter too is something per se one constituted under the specific notion of matter, per se contracting it. Indeed matter and this matter are not distinguished from the nature of the thing, as was shown above of any individual with respect to the common notion; therefore this matter cannot be intrinsically individuated through quantity, which is a thing distinct from it, nor through order to it, since rather this quantity expresses order to this matter than conversely. The second, about quantity, is evident, because of it too I shall inquire whence it is this, since it does not have this from its specific notion; and since one must not proceed to infinity, nor commit a vicious and useless circle, one will have to stop at some thing which is this by itself; therefore this is to be attributed to substance rather than to accident, since it is a prior and more absolute entity; or, if it is to be admitted that two incomplete beings are individuated through a mutual relationship to each other according to diverse genera of causes, this will rather have to be said of matter and substantial form among themselves than with some accident, because they are more per se connected and regard each other. Therefore all the arguments made can conclude the same of matter as they intend of form, for there is between them, as regards this, a certain equality. And on the other side matter surpasses form only in this, that it is a certain occasion of producing various and individual forms, as has been declared above; but form surpasses matter in this, that it chiefly constitutes the individual, and that it is more proper to it, and that matter is rather for the sake of form than conversely, as is said in Physics II, c. 9, text 91; therefore, all things weighed, the chief principle of individuation is the form.

Resolution of the question

7. This opinion, then, as it has been expounded by us, is sufficiently probable and comes very near to the truth. But simply it must be said that form alone is not the full and adequate principle of the individuation of material things, if we speak of their whole entity, although it is the chief one, and therefore according to a formal manner of speaking it is sometimes judged sufficient for the denomination of the same individual. All of which are to be declared and proved at length in sect. 6.