_Classification_ is an essential function, for the reasons already given, which it would be useless to repeat; but to classify is not to _realize intellectually,_ to understand, to grasp, to comprehend. If therefore, in life, we disapprove of those unmethodical people who detest classification, we do not disapprove any the less of the perpetual classifiers, who content themselves with arranging things in classes, when on the contrary the needful thing is to penetrate their nature and peculiar value. It is a very common error to believe that something has been thoroughly understood and every problem relating to it completely solved, when it has simply been put into a drawer, that is, into a class. Thus in the not distant past, instead of establishing whether the _Promessi Sposi_ were or were not an æsthetic work, and what movement of the spirit it represents, it was considered to be the duty of criticism to enquire whether that book were a romance or a novel, a historical or didactic romance, a historical representation of persons or of environment, and so on. The zoologist too, instead of studying the history and transformations of animals, their life and habits, limited himself to adding a rare specimen to a variety, or a variety to a subspecies, or a subspecies to a species, and believed that by so doing he had completely fulfilled the function of science. [Sidenote: _Interchange of the two, and genesis of perceptive and judicial illusions._] The abuse of empirical or classificatory judgments is not less in relation to perception, which, as we know, is nothing but the series of individual judgments. It frequently happens that when entering upon the discussion of real facts, and having in mind groups and series of pseudoconcepts, we hastily form empirical judgments, which take the place of pure individual judgments and are taken in exchange for them. From these exchanges have arisen certain famous controversies about the truth of perception, such as that indicated by the instance of the stick immersed in water, which seems to the eye to be broken, whereas it is whole and straight. The usual answer to such a view is that the error lies in the judgment, since perception as perception is never wrong. This answer is not altogether correct, since the perception is a judgment, and if the judgment is wrong, the perception also is wrong. On the contrary, the error is not in the judgment, but in the prejudice that the stick in question is in reality straight, and that when immersed in water the genuine reality is disturbed by a new element; as though the stick outside the water possessed greater or less reality than when immersed in the water. This error arises from the construction of the empirical concept of "stick," taken as a true and proper concept, so that when the stick is immersed in water and seems to be broken it seems not to answer to its true concept. Strictly speaking, the perception of the stick as broken or otherwise altered