It is shown from what has been said regarding the formal nature of the Idea, that only a history of Philosophy thus regarded as a system of development in Idea, is entitled to the name of Science: a collection of facts constitutes no science. Only thus as a succession of phenomena established through reason, and having as content just what is reason and revealing it, does this history show that it is rational: it shows that the events recorded are in reason. How should the whole of what has taken place in reason not itself be rational? That faith must surely be the more reasonable in which chance is not made ruler over human affairs, and it is the business of Philosophy to recognize that however much its own manifestations may be history likewise, it is yet determined through the Idea alone. Through these general preliminary conceptions the categories are now determined, the more immediate application of which to the history of Philosophy we have now to consider. This application will bring before us the most significant aspects in this history. a. _The development in Time of the various Philosophies._ The first question which may be asked in reference to this history, concerns that distinction in regard to the manifestation of the Idea, which has just been noticed. It is the question as to how it happens that Philosophy appears to be a development in time and has a history. The answer to this question encroaches on the metaphysics of Time, and it would be a digression from our object to give here more than the elements on which the answer rests. It has been shown above in reference to the existence of Mind, that its Being is its activity. Nature, on the contrary, is, as it is; its changes are thus only repetitions, and its movements take the form of a circle merely. To express this better, the activity of Mind is to know itself. I am, immediately, but this I am only as a living organism; as Mind I am only in so far as I know myself. _Γνῶθι σεαυτόν_, Know thyself, the inscription over the temple of the oracle at Delphi, is the absolute command which is expressed by Mind in its essential character. But consciousness really implies that for myself, I am object to myself. In forming this absolute division between what is mine and myself, Mind constitutes its existence and establishes itself as external to itself. It postulates itself in the externality which is just the universal and the distinctive form of existence in Nature. But one of the forms of externality is Time, and this form requires to be further examined both in the Philosophy of Nature and the finite Mind.