PROP. XII.————
In attempting to think it, we must leave out an element essential to its cognition, and therefore it cannot be thought of.and its qualities? And the answer is, that thought is unquestionably attempting to do this. It is attempting to leave out all conception of the ego, which was antecedently apprehended along with matter and its qualities,—and this it cannot do; for the ego required to be apprehended as the very ground (Proposition I.) and essential element (Proposition II.) of the original cognition. And therefore the thought of the antecedent ego must form part of the secondary representation, just as much as the knowledge of it formed part of the primary presentation. Consequently, all thought as well as all knowledge of matter per se is impossible.
How the imagination leads us astray.4. In the case of thought or representation, the imagination leads us into precisely the same inadvertency which we are led into by perception in the case of knowledge or presentation. When we perceive external objects, we usually pay so little attention to self that we seem to overlook altogether this most essential element of cognition: so when we think of, or represent, external objects, we think so little of the antecedent "me," formerly apprehended along with them, that we seem to be thinking of these objects themselves, without taking any notice of this, the necessary constituent in our original knowledge of them, and which is now a necessary constituent in our representation of them. The one oversight is the inevitable consequence of the other.