I think I hardly need recur to the suggestion that reality must be what is in space; for that would make our feelings unreal. Nevertheless reality to beings constituted as we are must appear spread out in space and in time. Yet the very fact that we know space as space and time as time, i.e. that we recognize the outside-one-another of things and the after-one-another of events, proves that in some sense or other (whether we can explain it or not) we are not in space and time. Space and Time exist for thought as forms in which we must perceive things. But if we ascribe to them an absolute existence, independent of any one's thought, we are speaking about what we cannot possibly know. Because if we did know them as absolutely existing, they would no longer exist absolutely. Thought cannot grasp anything outside itself, "outside thought" being simply a metaphorical way of saying "not thought about at all." My thought is, of course, incomplete; coming to know more of reality means that our thought comes to be more coherent, that it comes to itself.
Ordinary language does indeed always suggest a dualism of thought and things. Knowing is distinguished from the known. And the distinction is necessary for our ordinary thinking, which is picture-thinking, and takes different aspects as if they were separable in fact. But any philosophical theory of dualism raises more difficulties than it solves. If thought and reality are ultimately separated, then we have to face the question how they can be combined. How can we ever know anything, if thought and reality are ultimately distinct from one another? Scepticism is the logical outcome of dualism.
Is it necessary nowadays to discuss the idea of material substance as something existing apart from and independently of thinking? Matter either means (1) sensations and mental images referred in thought to past or future sensations — and this is what matter means to the ordinary person — or (2) it means the metaphysical hypothesis of an unknown and unknowable matter-in-itself. But if matter means sensations, present, past, and future, it can have no real existence except for a thinking being which can relate these sensations and images to one
