Page:Ferrier's Works Volume 1 - Institutes of Metaphysic (1875 ed.).djvu/321

RhPROP. XI.———— affirms that the mind can think of nothing but mere objects of sense; but the truth is, that the mind cannot think at all of mere objects of sense. It is, however, an undoubted truth that the mind can think only of what it can know or experience. For suppose it could think of something, at first hand, which it had never known; in that case the thing would be merely a known, instead of being a thought, thing; and the truth of the proposition would be in no degree compromised. It is impossible for any intelligence to take at second hand what it never had at first hand, because, whenever this happened, the thing so taken would be no longer taken at second, but at first, hand; instead of being thought, it would be known, and the law expressed in this proposition would be vindicated all the same. This is the whole truth of the philosophy which makes experience the source and mother of all that the mind of man can conceive.

4. The law which declares that representation must copy the data of presentation—that thought can walk only in the footsteps of an antecedent knowledge—is, in certain respects, not to be interpreted too strictly. Thought can alter the arrangement of the data of experience. It can mould the materials of knowledge into new combinations. This is called the play of the imagination, which at pleasure can fabricate representations of which