First, it assumes the possibility of ontological knowledge, by which we mean knowledge of being or substance apart from a mere succession of phenomena. The substance which is so known is matter. Now, since it is this statement that a belief in the possibility of ontological knowledge is an inherent necessity in all materialistic reasoning, which is the basis of our criticism, the statement must be examined more fully. Suppose for the moment that it is not such an inherent necessity — that it is possible to found materialism on something besides an ontological basis. If there be no knowledge of substance as such, there is either only knowledge of phenomena produced by the activity of the Ego (pure subjective idealism), or of phenomena entirely unrelated to any substance whatever (Humian scepticism), or of those related only to objective spirit (Berkeleian idealism), or of those related to an unknown and unknowable substance (H. Spencer), or of those brought into unity by the forms of knowledge which the mind necessarily imposes on all phenomena given in consciousness (as Kant), Now, since none of these can afford a sufficient basis for a theory, which posits matter as the universal underlying unity, we must admit that materialism exists on the basis of a belief in the possibility of ontological knowledge of such objective reality. If a materialist, who still believes that we have no knowledge of substance as such, replies that while we have knowledge of phenomena only, yet we know them as the effects of matter, the answer is obvious. Either we know this substance, matter, which is the cause of them, or we do not. If we do, it is ontological knowledge. If we do not, then it is as much assumption to claim that it is matter as it would be to name it mind. We must conclude, therefore, that a knowledge transcending phenomena is the sole thinkable basis for materialism.
Starting from this, we have to consider the relation of such, knowledge to materialism. What is involved in knowledge of matter as substance?
To know, requires something which knows. To know material phenomena, are required mental phenomena. A thing is for the mind non-existent until it is an idea or phenomenon of the mind. To know substance, matter, is required substance, mind. If materialism merely posited knowledge of material phenomena, there would be required to give it validity only mental phenomena,
