But hitherto the chief ill has been that useless and tiresome books are written. Matters begin to look graver when an approach is attempted between philosophical theories and empirical classifications and they are united in one treatise, as the _general_ part and the _particular_ part, the _abstract_ and the _concrete_ part, the _theoretical_ and the _historical_ part. We do not wish to refuse recognition to an occasionally just sense of the intimate relations between philosophy and history as among the motives that lead to such unions, the first of which flows into the second, revives it and is by it in turn revived. But the history, to which philosophy applies the torch, is all history in its palpitating reality; it is history represented by all histories that historians have written and will write, and also by those that they have not written and will not write. The history offered by these empirical descriptions is only a very small part of history and (what is worse) abstract and mutilated. This would, however, be an injury of not too grave a nature, even at this point, provided the incongruity were limited to literary unfitness; in which case, it is true, would be added to inutility the ugliness of a union capricious and artificial, but fortunately extrinsic. But by means of that extrinsic approach, the way is opened to the attempt at an intrinsic approach, and thus to the third form of the undue invasion of practical description by philosophy, which constitutes the _morbus philosophico-empiricus_ in all its harm fulness. [Sidenote: _Third form: attempt to place them in intimate connexion._] The attempt at intrinsic approach takes place when empirical classes are placed in connection with the philosophical concepts or categories, with pure thought. Nearly all philosophers have fallen into this error, since it is very natural that they should not have wished to leave a _hiatus_ between the first and second parts of their books of Philosophy of the practical, between the general and particular parts, and that they should have striven to connect the one with the other by passing logically from the concepts of the first to those of the second. The mistake was indubitably increased owing to their small degree of clearness as to the logical nature of the two orders of concepts (concepts and pseudo-concepts), which is fundamentally diverse, and we shall not further insist upon this matter. [Sidenote: _Science of the practical and Metaphysic: various significations._]