of matter_, apart from the properties which belong to it? We are under no necessity, then, of adopting the theory of "unisubstancisme," and we cannot found upon it in argument without building on a mere gratuitous assumption. IV. Our _fourth_ proposition is, That the same reason which warrants us in ascribing certain properties and phenomena to a distinct substance called "matter," equally warrants us in ascribing certain other properties and phenomena to a distinct substance called "mind;" and that the difference between their respective properties and phenomena is so great as to justify the belief that the _substances_ are different and ought to be denominated by distinctive names. When Materialists affirm, as they do, the existence of one only substantive being in Nature, and represent all our mental phenomena as the mere results of physical organization, they assume that "matter," at least, is a real _entity_; that it is a _substance_ or _substratum_ in which certain powers or qualities inhere; and that its existence, as such, is evident and undeniable. We are entirely relieved, therefore, by their own admission or assumption, from the necessity of discussing the more general problem of Ontology; the problem, whether we can prove the existence of _any_ being, properly so called, from a mere series of phenomena, a succession of appearances. They virtually admit, since they evidently assume, that the phenomena must have a substance under them, the qualities a substratum in which they inhere. Now, the very same reason which warrants, or rather obliges them to recognize "matter" as a substance and not as a shadow,--as an _entity_ which really exists and manifests itself by its properties and effects,--must equally warrant, or rather oblige them to recognize "mind" or "spirit" also as a distinct substantive being, unless it can be shown either that its properties are the same with those of matter, or that they may be accounted for by some peculiar modification of matter, some law of physical organization. There can be no reason for admitting the existence of "matter" as a substance, which does not apply also to the existence of "mind" as a distinct substance, if it shall be found that their properties are essentially different. We know, and can know, nothing of _substance_ otherwise than by its properties or powers: we know nothing of "matter,"--it would, in fact, be to us non-existent, but for its extension, solidity, and other properties; we know nothing of "mind,"--it would equally be to us non-existent, but for its consciousness, its thoughts, feelings, and desires; and if it be right to ascribe the one set of properties to a substantive being, called "matter," it cannot be wrong to ascribe the other set of properties also to a substantive being, called "mind."