But, though this is true, it is evident also that from pre-existing substances “a new compound nature” can be generated by the action of natural causes. These new compound natures are, indeed, called “new substances,” but they are the old substances under a new specific composition; that is, they are not new as substances, though they form a new specific compound. To say that such a compound is “a merely accidental aggregate of substances” is no objection. Were we to maintain that one single substance is an accidental aggregate of substances, the objection would be very natural; but to say, as we do, that one compound essence is an aggregate of substances united by accidental actions, is to say what is evidently true and unobjectionable. Yet we must add that the composition of such substances, accidental though it be to them individually, is essential to the compound nature; for this compound nature is a special essence, endowed with special properties dependent proximately on the special composition, and only remotely on the substantial forms of the component substances.
That there may be “no substantial difference” between two natural compounds is quite admissible; but it does not follow from the argument. It is admissible; because a different specific composition suffices to cause a different specific compound; as is the case with gum-arabic and cane-sugar, which consist of a different combination of the same components. Yet it does not follow from the argument; because the specific composition of different compounds may require, and usually does require, a different set of components—that is, of substances; which shows that there is also a substantial difference between natural compounds, although their essential form be not the substantial form of the peripatetics.
Lastly, we willingly concede that bread and flesh are not substantially identical; but we must deny that their substantial difference arises from their having a different substantial form. Bread and flesh are different specific compounds; they differ essentially and substantially, or formally and materially, because they involve different substances under a different specific composition. To say that bread and flesh are the same matter under two different substantial forms would be to give the lie to scientific evidence. This we cannot do, however much we may admire the great men who, from want of positive knowledge, thought it the safest course to accept from Aristotle what seemed to them a sufficient explanation of things. On the other hand, is it not strange that our opponents, who admit of no other substantial form in man, except the soul, should now mention a substantial form of flesh? To be consistent, they should equally admit a substantial form of blood, a substantial form of bone, etc. Perhaps this would help them to understand that the epithet “substantial,” when applied to characterize the forms of material compounds, has been a source of innumerable equivocations, and that the schoolmen would have saved themselves much trouble, and avoided inextricable difficulties, if they had made the necessary distinction between substantial and essential forms.
The arguments to which we have replied are the main support of the peripatetic doctrine; we, at least, have not succeeded in finding any other argument on the subject which calls for a special refutation. We beg, therefore, to conclude that the theory of strictly substantial generations, as well as that of the constitution of bodies, as held by the peripatetic school, rest on no better ground than “assumption,” or petitio principii, as Card. Tolomei reluctantly avows. There would yet remain, as he observes, the argument from authority; but when it is known that the great men whose authority is appealed to were absolutely ignorant of the most important facts and laws of molecular science, and when it is proved that such facts and laws exclude the very possibility of the old theory,[69] we are free to dismiss the argument. “Were S. Thomas to come back on earth,” says Father Tongiorgi, “he would be a peripatetic no more.” No doubt of it. S. Thomas would teach his friends a lesson, by letting them know that his true followers are not those who shut their eyes to the evidence of facts, that they may not be disturbed in their peripateticism, but those who imitate him by endeavoring to utilize, in the interest of sound philosophy, the positive knowledge of their own time, as he did the scanty positive knowledge of his.
But we have yet an important point to notice. The ancient theory is wholly grounded on the possibility of the eduction of new substantial forms out of the potency of matter; hence, if no truly substantial form can be so educed, the theory falls to the ground. We have already shown that true substantial forms giving the first being to the matter cannot naturally be educed out of the potency of matter.[70] This would suffice to justify us in rejecting the peripatetic theory. But to satisfy our peripatetic friends that we did not come too hastily to such a conclusion, and to give them an opportunity of examining their own philosophical conscience, we beg leave to submit to their appreciation the following additional reasons.
First, all philosophers agree that the matter cannot be actuated by a new form, unless it be actually disposed to receive it. But actual disposition is itself an accidental form; and all matter that has an accidental form has also a fortiori a substantial form. Therefore no matter is actually disposed to receive a new form, but that which has actually a substantial form. But the matter which has actually a substantial form is not susceptible of a new substantial form; for the matter which has its first being is not potential with regard to it, but only with regard to some mode of being. Therefore no new form truly and strictly substantial can be bestowed upon existing matter.
Secondly, if existing matter is to receive a new substantial form, its old substantial form must give way and disappear, as our opponents themselves teach, by natural corruption. But the form which gives the first being to the matter is not corruptible. Therefore no truly substantial form can give way to a new substantial form. The minor of this syllogism is easily proved. For all natural substances consist of simple elements, of which every one has its first being by a form altogether simple and incorruptible. Moreover, the substantial form of primitive elements is a product of creation, not of generation; the term of divine, not of natural, action; it cannot, therefore, perish, except by annihilation. The only form which is liable to corruption is that which links together the elements of the specific compound; but this is a natural and essential, not a strictly substantial, form.
Thirdly, the form which gives the first being to the matter is altogether incorruptible, if the same is not subject to alteration; for alteration is the way to corruption. But no form giving the first being to the matter is subject to alteration. For, according to the universal doctrine, it is the matter, not the form, that is in potency to receive the action of natural agents. The form is an active, not a passive, principle; and therefore it is ready to act, not to be acted on; which proves that substantial forms are inalterable and incorruptible. We are at a loss to understand how it has been possible for so many illustrious philosophers of the Aristotelic school not to see the open contradiction between the corruption of strictly substantial forms and their own fundamental axiom: “Every being acts inasmuch as it is in act, and suffers inasmuch as it is in potency.” If the substantial form is subject to corruption, surely the substance suffers not only inasmuch as it is in potency, but also, and even more, inasmuch as it is in act. We say “even more,” because the substance would, inasmuch as it is in act, suffer the destruction of its very essence; whereas, as it is in potency, it would not suffer more than an accidental change. It is therefore manifest that the corruption of substantial forms cannot be admitted without denying one of the most certain and universal principles of metaphysics.
Fourthly, if the natural agents concerned in the generation of a new being cannot produce anything but accidental determinations, nor destroy anything but other accidental determinations, then, evidently, the form which is destroyed in the generation of a new thing is an accidental entity, as also the new form introduced. But the efficient causes of natural generations cannot produce anything but accidental determinations, and cannot destroy anything but other accidental determinations. Therefore in the generation of a new being both the form which is destroyed and the form which replaces it are accidental entities. In this syllogism the major is evident; and the minor is certain, both physically and metaphysically. For it is well known that the natural agents concerned in the generation of a new substance have no other power than that of producing local motion; also, that the matter acted on has no other passive potency than that of receiving local motion. Hence no action of matter upon matter can be admitted but that which tends to give an accidental determination to local movement; and if any cause be known to exert actions not tending to impart local movement, we must immediately conclude that such a cause is not a material substance. On the other hand, all act produced belongs to an order of reality infinitely inferior to that of its efficient principle; so that, as God cannot efficiently produce another God, so also a contingent substance cannot efficiently produce another contingent substance; and a substantial form cannot efficiently produce another substantial form; but as all that God efficiently produces is infinitely inferior to him in the order of reality, so all act produced by a created substance is infinitely inferior to the act which is the principle of its production.[71] It is therefore impossible to admit that the act produced, and the act which is the principle of its production, belong to the same order of reality; in other terms, they cannot be both “substantial”; but while the act by which the agent acts is substantial, the act produced is always accidental. And thus it is plain that no natural agent or combination of natural agents can ever produce a truly substantial form.
A great deal more might be said on this subject; but we think that our philosophical readers need no further reasonings of ours to be fully convinced of the inadmissibility of the Aristotelic hypothesis concerning the constitution and the generation of natural substances. Would that the great men who adopted it in past ages had had a knowledge of the workings of nature as extensive as we now possess; their love of truth would have prompted them to frame a philosophical theory as superior to that of the Greek philosopher as fact is to assumption. As it is, we must strive to do within the compass of our means what they would have done much better, and would do if they were among the living, with their gigantic powers. We cannot hold in metaphysics what we have to reject in physics. To say that what is true in physics may be false in metaphysics is no less an absurdity than Luther’s proposition, that “something may be true in philosophy which is false in theology.”