Let us now inquire what is the legitimate meaning of these last words. A thing is said to exist in itself which not only has in itself what is needed for its own sustentation, but is moreover actually unsustained by anything lying under it, while it is itself the first subject of all its appurtenances. Such is the legitimate and traditional meaning of the words, “to exist in itself.” Hence substance may be legitimately defined as “a being which by its intrinsic constitution has no need of being supported by a subject, and which is not actually supported.”
A living author, however, in a valuable work to which I have no access at this moment, and from which, therefore, I do not make any quotation verbatim, asserts that substance “up to the present day” has always been understood to mean “a thing which by its intrinsic constitution has no need of being supported by a subject,” without taking into consideration its actual mode of existing. We shall presently show that this assertion is not true, and that this pretended definition is essentially incomplete. Meanwhile, let us observe that the precise difference between our definition and this new one consists in this only: that whilst the first presents substance as having no actual support, the second presents it as having no need of actual support, whether it be supported, at least supernaturally, or not. This difference, of course, would amount to nothing, and might be entirely overlooked, if things could not exist but in their natural condition; for anything which is in no need of support will naturally exist unsupported. [pg 003] But as philosophy is the handmaid of theology, we must remember that natural things can be raised to a supernatural state, and thus change their mode of existing; and in such a case the difference between the two said definitions may amount to much; because, if a thing which is naturally in no need of support be actually supported, then, according to the first definition, that thing thus actually supported would cease to exist as a substance, whilst, according to the second definition, it would still continue to exist as a substance, as it would still have no need of support. Hence the importance of ascertaining which of the two definitions we are authorized to hold according to the traditional doctrine of philosophers and theologians.
And first, Aristotle, at the head of the peripatetic school which held its sway for centuries, defines substance to be ultimum subjectum—“the last subject”—that is, the undermost subject; by which he unquestionably means that substance is something which not only lies underneath (subjacet), but is moreover the “last” thing which lies underneath. In other terms, substance, according to Aristotle, must have nothing lying under it, and, while supporting all its appurtenances, is itself actually unsupported. Hence it is, that quantity, for instance, though lying under some figure and supporting it, is no substance at all; for, though it is a subject, it is not the undermost.
This definition of the Greek philosopher has been universally accepted and made use of by Christian as well as pagan philosophers of all times, though many of them called the first subject what Aristotle had called the last—a change which does not affect the meaning of the definition, since what is last in the analytic is first in the synthetic process. It is clear, therefore, that both Aristotle and his followers do not define substance simply as that which has no need of support, but as that which is actually unsupported.
S. John Damascene, in the fourth chapter of his Dialectics, defines substance to be “that which is in itself in such a manner as not to exist in anything else”;[2] and after a few lines, “Substance,” he says, “is that which has its existence in itself, and not in anything else”;[3] and again in another chapter of the same work, “Substance,” he says, “is anything which subsists by itself and has its own being, not in any other thing, but in itself.”[4]
According to these definitions, which are identical, substance is a thing which not only is able to support itself, but actually supports itself to the exclusion of any other distinct supporter. This is quite manifest; for, if substance, in the opinion of this great doctor and philosopher, had been only a thing having no need of support, how could he require so pointedly and explicitly the actual mode of existing in itself and not in anything else?
S. Ambrose admits a notion of substance quite identical with that of Aristotle and of all the ancients, and employs it even in speaking of God himself. “God,” says he, “inasmuch as he remains in himself, and does not subsist by extrinsic support, is called a substance.”[5] [pg 004] God, of course, does not fall under the predicament of substance, as philosophers know; and yet the substantiality even of his nature, according to this holy doctor, implies the actual absence of extrinsic sustentation.[6]
S. Thomas, as we might expect, teaches the very same doctrine. “Substance,” says he, “is a thing whose quiddity requires to exist unsupported by anything else”—cui convenit esse non in alio;[7] and he adds that this formality (esse non in alio) is a mere negation; which is evident. And in another place, “Substance,” says he, “does not differ from being by any difference which would imply a new nature superadded to the being itself; but the name of substance is given to a thing in order to express its special mode of existing.”[8] Two things, then, or two constituents, are needed, according to S. Thomas, that we may have a substance: a physical being and a special mode of existing. The physical being is a positive reality, a nature perfectly constituted, both materially and formally, whilst the special mode is a mere negation; but, though a mere negation, is that which causes the thing to be a substance, as the name of substance is given to the thing in order to express its special mode of existing. Therefore the thing itself apart from such a special mode cannot be a substance, any more than a six-pence apart from its rotundity can be a circle.
Toletus includes in his definition of substance both the thing and the special mode of existing. He says: “The first substance is a sensible nature which is not predicated of any subject nor exists in any subject.”[9]
Suarez says even more explicitly, “It is not necessary for the essence of substance that it should have its own subsistence, but that it should have the mode of substance.”[10] We cannot, then, overlook, and much less discard, this special mode without destroying the essential notion of substance as such. Now, he who defines substance to be simply a thing which has no need of support overlooks and discards this special mode; hence he destroys the essential notion of substance as such.