“ Matter, in other words, must be assumed to exist, though mind cannot know it in itself. From this question there emerges a second and more difficult problem. Consciousness, it is held, is of two main kinds, sensation and reason. ”

“ To the first problem there is one obvious and conclusive answer, namely that matter in itself is inherently unthinkable and comes within the vision of the mind only as an intellectual presentation. It follows that philosophy is in a sense both dualist and monist; it is a cosmic dualism inasmuch as it admits the possible existence of matter as a hypothesis, though it denies the possibility of any true knowledge of it, and is hence in regard of the only possible knowledge an idealistic monism. ”

“ On the other hand is a hypothetical dualism, according to which it is held that mind cannot bridge over the chasm so far as to know matter in itself, though it is compelled by its own laws of cause and effect to postulate matter as the origin, if not the motive cause, of its sensations. It follows that, for the thinking mind, matter is a necessary hypothesis. Hence the theory is a kind of monism, inasmuch as it confessedly does not assert the existence of matter save as an intellectual postulate for the thinking mind. ”