Cursus Philosophicus Thomisticus, Secunda Pars Philosophiae Naturalis

The whole difficulty among the ancient philosophers concerning the investigation of substantial generation consisted in their inability to understand prime matter as being in potency to being absolutely, while nevertheless being a being in reality in itself. Consequently, they could not understand substantial form as giving matter being absolutely, namely, first being itself. For in that case matter would lack all being of itself and consequently would not be a being; but a being does not come from nonbeing, because nothing comes from nothing, as the Philosopher discusses at length in Physics I,¹ in this book, On Generation and Corruption I,² and Metaphysics XI, ch. 6.³ Thus we said in Physics III, q. 3,⁴ that unless matter is posited as a being in potency in such a way that it lacks every entitative being of itself, we have no principle by which to show that there is a substantial form that gives first being, which is being absolutely and substantial being.

From this it is entirely clear that Aristotle and St. Thomas, who follows him, were wholly unaware of the claim that prime matter has of itself an entitative act and incomplete existence. The ancients thought that matter was nonbeing and absolutely nothing precisely because it was a being in potency, as is clear from the Philosopher in this book, On Generation and Corruption I, text 12,⁵ where he says, “This above all is what the ancient philosophers feared when they assigned an account of substantial generation: that something might be generated from preexisting nothing.” Explaining this, St. Thomas says there, lecture 6, near the end,⁶ “The first philosophers especially feared that something might be generated from nothing preexisting; for what is not a being in act is nothing. Thus it seems that there could not be generation absolutely in this way, namely, that substance be generated from what is not a being in act but is a being in potency.” The ancients therefore thought that matter, precisely because it was a being in potency, was nothing and consequently lacked an entitative act or partial existence. For if matter had that, it would be quite consistent for it to be a being in potency with respect to forms and yet not be nothing, since in order to be nothing it must lack every existence, even partial existence. But the ancient philosophers inferred that if something was a being in potency and not in act, it was nothing; therefore they thought that if matter was a being in potency, it lacked all being, even partial being. Aristotle, rejecting this view of the ancients, does not say that matter has an entitative act or existence although it is in potency to forms. Rather, he says that matter is not nothing but exists insofar as it is under different forms, which is why the generation of one thing is the corruption of another. Thus generation occurs per se from a being in potency, but per accidens from a being in act: for it is per accidens to generation that matter existed under this or that form, which is corrupted and through which matter has being in act, as he teaches in Physics I, text 66,⁷ and On Generation and Corruption I, text 17,⁸ as St. Thomas explains there, lecture 7, near the end.⁹ But if matter, insofar as it concurs in generation per accidens, is a being in act—that is, through the form that is corrupted—Aristotle plainly presupposes that matter of itself does not have an entitative act or partial existence. Otherwise generation would occur per se from a being in act, since matter would exist or be a being in act not through the form but through its own entity.

Thus the principle for showing against the ancient philosophers that substantial generation occurs and that substantial form is introduced into matter is drawn from only two sources. First, from being, which distinguishes substance from accident—namely, per se being, which is primary and underlies other things. For if substantial generation occurs, it must give per se being and introduce a form that gives such being. Second, the principle is drawn from substantial corruption, which is opposed to generation. For if corruption occurs, so does substantial generation.

Proceeding in the first way, one must necessarily take as the principle that matter is a being in potency without any entitative act. For substantial generation is presupposed to be that by which substantial being is acquired, or by which a thing becomes a being absolutely. Since the ancients said that whatever is a being must be a being in act, they consequently inferred that if generation presupposes some being as its subject, it must presuppose a being in act. Thus no generation could produce substantial being itself—that is, primary and foundational being, which is substantial. Since, in accordance with Aristotle’s principles, we admit that nothing comes from nothing and, in turn, that substantial generation makes a being absolutely by giving it primary and substantial being, we must say that the subject from which substantial generation occurs, namely prime matter, is neither nothing nor a being in act of itself, but a being in potency per se and in act through another, namely through form.

But if matter is once posited as a being in act of itself and as existing through an entitative act, one cannot prove against the ancients that the form coming to it is substantial and that generation is substantial, giving first and complete being, unless one proves against them that even if partial being is presupposed in matter, substantial being can result for it through the form that comes to it and the parts themselves can be substantially united. But Aristotle provides no principle for this, nor can one be given without begging the question. For it cannot be established against those who deny substantial generation and substantial form—as the ancients did when they said that matter is the whole substance of a thing—that some form and action are substantial except by reference to the substantial being they provide, namely the primary being that underlies everything. But if they presuppose some partial being in matter, this path is closed and the principle weakened. For how can one prove that the being given by the form is primary and substantial if it presupposes another being in the matter to which the form comes? If one says that this being is partial, that is precisely what remained to be proved, and it begs the question. For the ancients denied that there is a substantial form and held that matter is the whole substance of a thing. How, then, can one prove that those partial beings belong to prime matter and to form in such a way that together they constitute generation absolutely? If some integral part is produced and joined to another that already has being, that change will be adgeneration, not first generation, because it presupposes some prior being. Likewise, if being is presupposed in matter and the form produced adds another being to it, even if partial, one cannot prove that this is generation absolutely, because its substantiality cannot be proved from the very first being on which that proof must rest, since some being is presupposed in matter. Thus the ancients would say that form does not give first being and being absolutely, but adds to or adgenerates upon a presupposed being.

In our view, however, since there is only one being, which belongs to the composite through form as its principle and actualizes matter, to give being to the composite through form is the same as giving it first being and being absolutely. On the other hand, one cannot prove against the ancients that the two parts—matter and form—are substantial unless one either presupposes these parts, which they denied (and so begs the question), or proves them substantial because they are necessary for generation and corruption. But that again is what they denied: they denied substantial generation and corruption, admitting only alteration, which makes latent forms appear or hides them. Therefore, unless one says that form gives first being itself and consequently that matter is in potency to form in such a way that it presupposes no being in itself but has all its being through form, substantial generation cannot be proved against the ancients.

The second principle proves that substantial generation occurs, namely, from corruption itself. For it is clear that substantial corruption occurs; therefore generation must occur.

The inference is sound: if forms are substantially corrupted when they cease to be, then they are substantially generated when they begin, and do not merely appear anew; otherwise, when they cease, they would merely be hidden. The premise is proved both because, if there were no substantial corruption, every substance would be incorruptible in its substantial being, and because if a form is not corrupted but remains in matter or is not distinct from matter, then its proper attributes would remain as well. There would be no reason for us to preserve the proper attributes while the form and nature to which they belong remained. But it is clear that when an animal dies, its sensory powers do not remain in the earth or fire into which it is converted. Nor can one say that these powers remain there impeded and hidden; for then, if fire had the power of sight and hearing but these were impeded, fire would be blind and deaf, since it would possess these powers under impediment. Finally, it is clear that substantial corruption occurs in a human being because, when the person dies, the soul remains separated from the body. Otherwise the human being would not die if the soul remained united to matter, and the human being would be substantially incorruptible. For the soul is neither hidden in matter nor drawn out from it, but comes from outside. Therefore, when the soul departs, a new form must begin to exist in matter through true generation, since the form it had is substantially separated from it.

Other authors commonly offer further proofs, but they have little force against the ancients—for example, that prime matter is in passive potency to all forms, that there are different substantial forms, and that different accidents and operations must follow different forms, since matter of itself is indifferent to all things.

These arguments beg the question, because what the ancients denied was precisely that there are substantial forms or that accidents follow a form newly arriving in matter, rather than merely appearing anew in matter in which they were latent of themselves. They said that matter was a being in act and did not need a substantial form to give it first and substantial being, but only one presupposing matter’s existence. Thus every form newly arriving would be accidental, because it would not have the proper character of substance, which implies first being that underlies other things. Therefore, unless one affirms that matter is a being in potency in such a way that it also has first being through form, these proofs are emptied of force.

Against substantial generation explained in this way, there are few difficulties. The argument of the ancients that moved them has no force. They said there could not be a form that gives first being, as substantial being must be, for such a form would come to a subject having no being at all, since form gives first being to its subject. Therefore that subject would be nothing, and thus something would simply come from nothing—which is not generation but creation.

To this we reply, following the teaching of Aristotle and St. Thomas, that prime matter is neither nothing nor a being in act, that is, existing per se by reason of its own entity. Rather, it exists through another, namely through form. Thus of itself it is a being capable of existence as well as of form, although it is neither form itself nor existence itself. What is capable of existence is truly a being and is not nothing in the contradictory sense opposed to being, because nothing is capable of existence neither per se nor through another. Matter, however, truly exists as subject to form, though not without form. Indeed, even the substantial composite itself does not exist or operate without a mode of subsistence and without accidents.

Second, you will object: In the substance that is generated, only essence and existence are found. Essence cannot come to be, because when existence is removed, only essential predicates remain, which are eternally true and independent of time. Existence, however, is not substance, but something that belongs to substance accidentally, on the assumption that it is distinct from substance. Indeed, the very act of generation is an accident in the category of action; therefore its term is an accident.

We reply that essence is not made or produced with respect to the essential connection of predicates taken objectively; in this way it is an eternal truth. But subjectively, as existing in itself, the essence and substance itself is produced as the subject of existence, so that essence is related as the existing thing, while existence is that by which it exists, as the actual term of production and of being outside its causes. Although existence is said to belong accidentally, it is not so as a predicamental accident, but as an accidentally predicable mode or term of substance, since it is reduced to the category of substance. In reality, however, essence itself is produced as the subject of existence—not separately from existence, nor separately from production, but through it. Nature is not produced separately from the composite or supposit, but in it. Essence insofar as it is subject to existence is temporal, not eternal or an eternal truth, because existence and the subjection of essence to existence are given through a temporal action. Generation is formally an accident in the category of action, but terminatively it regards substance, since it proceeds from the generative potency by the power of substance. Therefore it is an accident, yet it tends toward producing substance.

Finally, it is argued: If one generation succeeds another, it follows that things diverse in species share the same matter, and therefore are not substantially and in every respect diverse. Likewise matter will belong to different species, now to one and now to another, according to the different forms with which it is united. Thus it will not remain simply the same, since it derives its actuality and species from form.

We reply that there is no difficulty in things diverse in species having matter in common, as they do, though not by being informed simultaneously but successively, because matter is thus capable of all forms and in potency to them. They do not therefore share the same matter numerically; rather, the same matter, according to its potentiality, serves different forms in different composites, one form successively excluding another and constituting a different composite. There is no difficulty in this. Nor is there any difficulty in matter, through being informed, participating successively in different species of forms and constituting different composites, because it is in potency to them. Of itself it has only potential entity, which it does not receive from form; rather, by receiving forms in itself, it is actualized by them and reduced in act to the species by which it is informed. Since matter is a part of the species and of the composite it constitutes, it can be reduced in act to many species, because it is in potency to all of them.