In matter, as we know it, there are two elements. There are certain sensations, or certain qualities which we come to know by sensation, and there are certain relations. Now, with regard to the sensations, a very little reflection will, I think, show us that it is absolutely meaningless to say that matter has the qualities implied by these sensations, even when they are not felt, and would still possess them, even supposing it never had been and never would be felt by any one whatever. In a world in which {9} there were no eyes and no minds, what would be the meaning of saying that things were red or blue? In a world in which there were no ears and no minds, there would clearly be no such thing as sound. This is exactly the point at which Locke's analysis stopped. He admitted that the 'secondary qualities'--colours, sounds, tastes--of objects were really not in the things themselves but in the mind which perceives them. What existed in the things was merely a power of producing these sensations in us, the quality in the thing being not in the least like the sensations which it produces in us: he admitted that this power of producing a sensation was something different from, and totally unlike, the sensation itself. But when he came to the primary qualities--solidity, shape, magnitude and the like--he supposed that the qualities in the thing were exactly the same as they are for our minds. If all mind were to disappear from the Universe, there would henceforth be no red and blue, no hot and cold; but things would still be big or small, round or square, solid or fluid. Yet, even with these 'primary qualities' the reference to mind is really there just as much as in the case of the secondary qualities; only the fact is not quite so obvious. And one reason for this is that these primary qualities involve, much more glaringly and unmistakably than the secondary, something which is not _mere_ sensation--something which {10} implies thought and not mere sense. What do we mean by solidity, for instance? We mean partly that we get certain sensations from touching the object--sensations of touch and sensations of what is called the muscular sense, sensations of muscular exertion and of pressure resisted. Now, so far as that is what solidity means, it is clear that the quality in question involves as direct a reference to our subjective feelings as the secondary qualities of colour and sound. But something more than this is implied in our idea of solidity. We think of external objects as occupying space. And spaciality cannot be analysed away into mere feelings of ours. The feelings of touch which we derive from an object come to us one after the other. No mental reflection upon sensations which come one after the other in time could ever give us the idea of space, if they were not spacially related from the first. It is of the essence of spaciality that the parts of the object shall be thought of as existing side by side, outside one