Again, perhaps you will maintain that the faculty of hearing may be thought of as something which exists anterior to the existence or application of sound; and that, being thought of as such, it must be conceived independently of all conception of its object, sound being, ex hypothesi, not yet in rerum natura. But let any one attempt to frame a conception of such an existence, and he will discover that it is possible for him to do so only by thinking back in union with that existence, the very sound which he pretended was not yet in thought or in being. Therefore, in this and every other case in which we commence by thinking the subjective of any perception, we necessarily blend with it the objective of that perception in one indivisible thought. It is both of these together which form a conceivability. Each of them, singly, is but half a thought, or, in other words, is no thought at all; is an abstraction, which may be uttered, but which certainly cannot be conceived.
We have now completed the construction of our premises. One or two condensed sentences will show the reader the exact position in which we stand. Our intercourse with the external universe was the given whole with which we had to deal. The older philosophies divided this given whole into the external universe on the one hand, and our perceptions of it on the other; but they were never able to show how these two, the objective and the subjective, could
