All the definitions that have ever been given of philosophy will be found to contain the thought that philosophy is the pure concept (or to say the same thing with more words and less precision), that it has the pure concept as its directive criterion. All, be it well understood, save those which, in negating the pure concept, negate also the peculiar nature of philosophy. But such are not, properly speaking, definitions of philosophy, although even these, by contradicting themselves, imply and assume the definition of philosophy as an original form, and so as the pure concept. Such is the case with the theories already examined, of æstheticism, mysticism, and empiricism (and also of mathematicism), to which we shall return. For them, philosophy is art, sentiment, the empirical (or abstract) concept. But it is an art in some way differentiated from the rest of art, a sentiment that acquires a peculiar value, an empirical or abstract concept, which raises itself up and looks over the heads of the others. Thus it is something peculiar, a mode of reflecting _sui generis,_ and so precisely the pure concept. Empiricism especially reveals this intimate contradiction, when it advocates a philosophy consisting of a systematization or synthesis of the results of the empirical sciences. That is to say, it advocates something not given by the empirical sciences, because, were they to give it, they would already be systematized and synthesized of themselves, and the further elaboration asked for would be altogether superfluous. [Sidenote: _Those that define it as the science of supreme principles, ultimate causes, etc.; contemplation of death, etc.;_] All the other definitions which presuppose the peculiarity of philosophy are reducible, as is easily seen, to the single character of the pure concept. Philosophy (they say) is the science of the _supreme principles of the real,_ the science of _ultimate causes,_ of the _origin of things,_ and the like. In these propositions, the supreme principles are evidently not real things, or groups of real things, or empty formulæ, but the ideal generators of the real. Ultimate causes are not causes (for the cause is never ultimate, being always the effect of an antecedent cause), but ideal principles. The origin in question is not the historical origin of this or that single fact, but the ideal deduction of the fact from facts or from omnipresent reality. The same idea is expressed in the imaginative saying that philosophy is the _contemplation of death._ For what but the individual dies? And is not the contemplation of the death of the individual also that of the immortality of the universal? Is it not contemplation of the eternal? This remark supplies the motive for that other formula which defines philosophy as "the vision of things _sub specie aeterni._" [Sidenote: _as elaboration of the concepts, criticism, science of norms;_]