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. 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_.