We have now arrived at something which is just as true when your perception is illusory as when it is correct. If you say “a visual black dot is occurring”, you are speaking the truth, if there is one in your field of vision. We have eliminated the suggestion that others could see it, or that it could be touched, or that it is composed of matter in the sense of physics. All these suggestions are present when one says, in ordinary conversation, “there is a black dot”; they are intended to be eliminated by the addition of the word “visual” and the substitution of “is occurring” for “there is”. By these means we have arrived at what is indubitable and intrinsic in the addition to your knowledge derived from a visual datum. We must now ask ourselves once more: Is there still a distinction, within what is immediate and intrinsic, between the occurrence of a visual datum and the cognition of it? Can we say, on the basis of immediate experience, not only “a visual black dot occurs”, but also “a visual black dot is cognised”? My feeling is that we cannot. When we say that it is cognised, we seem to me to mean that it is part of an experience, that is to say, that it can be remembered, or can modify our habits, or, generally, can have what are called “mnemic” effects. All this takes us beyond the immediate experience into the realm of its causal relations. I see no reason to think that there is any duality of subject and object in the occurrence itself, or that it can properly be described as a case of “knowledge”. It gives rise to knowledge, through memory, and through conscious or unconscious inferences to the common correlates of such data. But in itself it is not knowledge, and has no duality. The datum is a datum equally for physics and for psychology; it is a meeting point of the two. It is neither mental nor physical, just as a single name is neither in alphabetical order nor in order of precedence; but it is part of the raw material of both the mental and the physical worlds. This is the theory which is called “neutral monism”, and is the one that I believe to be true. CHAPTER XX CONSCIOUSNESS?