the act of apprehension. Either of these might be called an “idea”; probably either would have been called an idea by Berkeley. The act is undoubtedly in the mind; hence, when we are thinking of the act, we readily assent to the view that ideas must be in the mind. Then, forgetting that this was only true when ideas were taken as acts of apprehension, we transfer the proposition that “ideas are in the mind” to ideas in the other sense, i.e. to the things apprehended by our acts of apprehension. Thus, by an unconscious equivocation, we arrive at the conclusion that whatever we can apprehend must be in our minds. This seems to be the true analysis of Berkeley’s argument, and the ultimate fallacy upon which it rests.
This question of the distinction between act and object in our apprehending of things is vitally important, since our whole power of acquiring knowledge is bound up with it. The faculty of being acquainted with things other than itself is the main characteristic of a mind. Acquaintance with objects essentially consists in a relation between the mind and something other than the mind; it is this that constitutes the mind’s power of knowing things. If we say that the things known must be in the mind, we are either unduly limiting the mind’s power of knowing, or we are uttering a mere tautology. We are uttering a mere tautology if we mean by “ in the mind” the same as by “ before the mind,” i.e. if we mean merely being apprehended by the mind. But if we mean this, we shall have to admit that what, in this sense , is in the mind, may nevertheless be not mental. Thus when we realize the nature of knowledge, Berkeley’s argument is seen to be wrong in substance as well as in form, and his grounds for supposing that “ideas”— i.e. the objects apprehended—must be mental, are found to have no validity whatever. Hence his grounds in favour of idealism may be dismissed. It remains to see whether there are any other grounds.
It is often said, as though it were a self-evident truism, that we cannot know that anything exists which we do not know. It is inferred that