The natural sciences have nothing to do with a philosophic knowledge of nature as will, with a Philosophy of the practical. They are, as has already been said, not knowledge of will, but will; not truth, but utility. In consequence of this, they extend to the whole of reality, theoretic and practical, to the products of the theoretic spirit, not less than to those of the practical spirit; and without knowing any of them, universally or individually, they manipulate and classify them all in the way we have seen. They have not therefore a _special object,_ but _a special mode of treatment,_ their object or matter being the presupposed philosophic-historical knowledge of the real. They do not treat of the material and mechanical aspect of the real, nor even of its non-theoretical, practical, volitional aspect (or what is incorrectly called the irrational aspect of it). They turn the theoretical into the practical, and by killing its theoretic life, make it dead, material, and mechanical. Nature, matter, passivity, motion _ab extra,_ the inert atom and so on, are not reality and concepts, but natural science itself in action. Mechanism, logically considered, is neither a fact nor a mode of knowing the fact. It is a non-fact, a mode of not-knowing: a practical creation, which is real only in so far as it becomes itself an object of knowledge. This is the _gnoseological_ or _gnoseopractical_ meaning of the word "nature," a meaning which must be kept carefully distinct from the two preceding meanings. When we speak, for instance, of _matter_ or of _nature_ as not existing, we mean to refer to the puppet of the naturalists, which the naturalists themselves and the philosophers of naturalism, forgetting its genesis, take for a real if not a living being. That matter (said Berkeley) is an abstraction; it is (say we) an empirical concept, and whoever knows what empirical concepts are will not pretend that matter or nature exists, simply because it is spoken about. [Sidenote: _The illusions of materialists and dualists._]