The world of perception has made its impression, and thereby laid the foundation of all the subsequent thoughts of the individual. He may by reflection make clearer what he has apprehended; he may yet acquire much knowledge as nourishment for the fruit which has once set; he may extend his views, correct his conceptions and judgments, it may be only through endless combinations that he becomes completely master of the materials he has gained; indeed he will generally produce his best works much later, as the greatest heat begins with the decline of the day, but he can no longer hope for new original knowledge from the one living fountain of perception. It is this that Byron feels when he breaks forth into his wonderfully beautiful lament: “No more—no more—oh! never more on me The freshness of the heart can fall like dew, Which out of all the lovely things we see Extracts emotions beautiful and new, Hived in our bosoms like the bag o’ the bee: Think’st thou the honey with those objects grew? Alas! ’twas not in them, but in thy power To double even the sweetness of a flower.” Through all that I have said hitherto I hope I have placed in a clear light the important truth that since all abstract knowledge springs from knowledge of perception, it obtains its whole value from its relation to the latter, thus from the fact that its conceptions, or the abstractions which they denote, can be realised, _i.e._, proved, through perceptions; and, moreover, that most depends upon the quality of these perceptions. Conceptions and abstractions which do not ultimately refer to perceptions are like paths in the wood that end without leading out of it. The great value of conceptions lies in the fact that by means of them the original material of knowledge is more easily handled, surveyed, and arranged. But although many kinds of logical and dialectical operations are possible with them, yet no entirely original and new knowledge will result from these; that is to say, no knowledge whose material neither lay already in perception nor was drawn from self-consciousness. This is the true meaning of the doctrine attributed to Aristotle: _Nihil est in intellectu, nisi quod antea fuerit in sensu_. It is also the meaning of the Lockeian philosophy, which made for ever an epoch in philosophy, because it commenced at last the serious discussion of the question as to the origin of our knowledge. It is also principally what the “Critique of Pure Reason” teaches. It also desires that we should not remain at the _conceptions_, but go back to their _source_, thus to _perception_; only with the true and important addition that what holds good of the perception also extends to its subjective conditions, thus to the forms which lie predisposed in the perceiving and thinking brain as its natural functions; although these at least _virtualiter_ precede the actual sense-perception, _i.e._, are _a priori_, and therefore do not depend upon