So far as Darwinism is an attempt to show that the classes of plants and animals are not a mere juxtaposition and aggregation, but are to be explained by reference to a single genetic principle, it is in harmony with the Evolution taught by Schelling and Hegel. Both alike overthrow the hard and fast lines of division which semi-popular science insists upon, and restore the continuity of existence. Both regard Nature as an organic realm, developing by action and re-action within itself, living a common life in thorough sympathy and solidarity, and not a mere machine in which the several parts retain without change the features and functions impressed upon them at creation by some supernal architect. But they differ in other points. Ordinary Darwinism, at least, talks as if circumstances and organism were independent originally, and only brought as it were, incidentally, in contact and correlation. It fails to keep hold of the fact--of which it is abstractly aware--that the two act upon and modify each other because they are members of a larger organism. It forgets, in short, what Schelling so thoroughly realised, that the organic and inorganic, ordinarily so called, are both in a wider sense organic. It wants the courage of recognising its own tacit presuppositions. But the characteristic difference between the evolution theory of to-day and that meant by the philosophers is different from this, though connected with it. 'The assertion,' says Schelling, 'that the various organisms have formed themselves by gradual development from one another, is a misconception of an Idea which really lies in reason[8].' And Hegel no less decidedly asserts that 'Metamorphosis' (as the term was then applied, e. g. by Goethe, to what we now call Evolution) really _exists_ as a fact only in the case of the living individual,--not in the supposed or theoretical continuity of the species. 'It is an awkward way both ancient and modern speculative biology have had of presenting the development and transition of one physical form and sphere into a higher one as an outwardly-actual production,--which, however, in order to make it clearer, has been thrown back into the darkness of the past.'[9] Yet notwithstanding these and even later protests, there is a great charm for many minds in the evolutionist picture, e. g., of the horse of to-day as the literal descendant through nearly fifty great stages (called species) from some creature of the eocene age, which gradually transformed itself in consequence of innate instability or variability of construction and in obedience to changes in its environment. But whatever value there may be in these as yet hypothetical aids to the imagination in grasping and unifying the variety of organic life, they run on another line from the philosophical evolution. That evolution is in the _Idea_, the _Notion._ It is the 'fluidity' of terms of thought that is here sought, not of the kinds of things,--except in a secondary way.