the logical character which they wrongly assumed. But they cannot be discarded, unless we are willing to throw away the gold, through our unwillingness to have the trouble of separating it from the dross. And this necessity for purification further confirms the error of the philosophism, since it is the purification of Philosophy and of History from the Philosophy of History. [Sidenote: _Philosophy of nature._] Another manifestation of the philosophism, somewhat different from the preceding, is the science which assumes the name of _Philosophy_ of _nature._ Here it is claimed to deduce, not the historical facts themselves, but the general concepts, which constitute the natural sciences. The philosophy of nature can be considered as the converse error to the empiricist error, which claims to induce philosophic categories _a posteriori,_ whereas this claims to deduce empirical concepts _a priori._ [Sidenote: _Its substantial identity with the Philosophy of history._] But the theoretic content of empirical concepts and of the natural sciences is, as we know, nothing but perception and history. So that, in the final analysis, the Philosophy of nature can be reduced to the Philosophy of history (extended to so-called inferior or subhuman reality), making, like the other, the vain attempt to produce in the void what thought can produce only in the concrete, that is to say, by synthesizing. And that it tends to become a Philosophy of history is also to be seen from its not infrequent hesitances before abstract concepts, or mathematical science, sometimes declaring that the pure abstractions of the intellect must remain such and are not otherwise deducible and capable of being philosophized about. The Philosophy of nature has usually been extended to the field of the physical and natural sciences, including also some parts of mechanics. But it has refused to undertake the deduction of the theorems of geometry and still more the operations of the Calculus. [Sidenote: _The contradictions of the Philosophy of nature._]