And above all, philosophy does not deal with a problem in time, with a mere sequence; if it deals with a history of nature, the agents of that history are powers and forces--and powers which are ideal no less than real. A nearer approach to the philosophic conception is to be found in the views which modern physiology takes of the nature of organic structure and function[10]. In the simplest phases of protoplasm, the apparently homogeneous mass is really undergoing a series of changes, and indeed only exists as such, because it is the ever-renewed resultant of two correlated processes,--a movement up (anabolic change) by which dead matter is assimilated and built into it, and a movement down (katabolic changes) by which its composing elements are disintegrated and left behind, with accompanying liberation of energy. Protoplasm or 'living matter' is the incessantly formed and re-formed thin line on which these two currents for the moment converge,-a temporary crest of white foam, as it were, raising itself on the Heraclitean wave of vicissitude, where all things flow on and nothing abides. But wherever protoplasm arises and maintains itself on this borderline of ascending and descending states, it exhibits the three well-known properties of assimilation, contractility, and sensitiveness. Protoplasm, placed as it were in the mean between these two processes, is or has the synthetic power which governs them and keeps them in one. It is no mere chemical substance, undergoing composition and decomposition, but rather, if looked at from the somewhat speculative standpoint of molecular physics, a kind of intricate movement or dance of particles, a shape or 'form' instinct with the power of producing and reproducing itself, and, ultimately, in some highly differentiated phases (nerve-system), with a power of producing and reproducing a world of imagination. A philosophy of Nature is only half a philosophy. Its purport is to set free the spirit in nature, to release intelligence from its imprisonment in material encasements which hide it from the ordinary view, and to gather together the _disjecta membra_ of the divine into the outlines of one continuous organisation. It seeks to spiritualise nature, i. e. to present the inner idea, unity, and genetic interdependence of all its phenomena: to delineate _natura formaliter spectata_ not as a logical skeleton of abstract categories, but in its organisation and continuous life. There remains the problem of what Schelling calls 'Transcendental Idealism':--called 'transcendental' to avoid confusion with the vulgar idealism which supposes the world to be what it calls a mere 'idea' or phantom of the mind. Schelling's is on the contrary an 'Ideal-Realism': it 'materialises the laws of intelligence to laws of nature[11].'