The metaphysic which towards the beginning of the nineteenth century grew out of the Kantian idealism was a radical criticism of the philosophy that underlay the Enlightenment and the Revolution. Oblivious of its own true character, the thought had, as it were, materialized itself into a barren universalism, a tissue of abstract humanitarian ideals: it now sprang into new .life with the rediscovery of its own historical nature and of the concrete and individual character of its development. Among the greatest achievements of this metaphysic was the recognition of the national character of thought.This was no mere acquiescence in a narrowly parochial outlook; it was something much deeper, namely the realization that humanity in general only exists in individuals, and that only in the acquisition of concrete individual form can the mind achieve its true universality. This constituted a great step in advance: indeed, it was premature, appearing as it did only a few years after the declaration of the Rights of Man.Even its authors were blind to its full significance, and very soon obscured it altogether Hegel with a misdirected spirit of patriotism which made Germany the center of the world: the historical school of jurisprudence by relapsing into a kind of Platonism and losing itself in a world of vague and sentimental ideals.The subsequent development of philosophy was not in keeping with this starting-point: although it maintained the absolutely concrete and historical character of thought, it nevertheless sullied its stream by carrying with it the undissolved residue of the old abstract philosophies. The naturalism which reasserted itself after the speculative movement of Kant and Hegel is a sure symptom of that internal conflict in which thought is involved when confronted by unsolved problems; but the peculiar thing about naturalism is that it expresses the conflict in the form of a dogma, and offers as a definite solution what is really the incipient doubt, which becomes more definite as the problem takes shape.The beginnings of naturalism are to be traced back to the Hegelian philosophy itself, in which the merely mechanical development of the dialectic in many parts of the system and the introduction of the caput mortuum of the philosophy of nature simply concealed the unsolved problems of which they claimed to be the solutions. But we can observe this still better in the philosophy immediately following Hegel, as we shall very soon see. The completest form of modern naturalism is the product of the empirical sciences, and especially biology.