FORE:An energy continually advancing through successive gradations, and diminishing as it advances��such, as we have seen, is the conception of existence offered by Plotinus. We have seen, also, how to explain the genesis of one principle from another without the aid of supernatural volition or of mechanical causation, he is compelled to press into the service every sort of relationship by which two objects can be connected, and to invest it with a dynamical significance which only the phenomena of matter and motion can possess. But what he chiefly relies on for guidance in this tortuous labyrinth of timeless evolution, is the old Greek principle that contraries are generated from one another. And with him, as with the earlier thinkers, all contraries reduce themselves, in the last analysis, to the four great antitheses of the One and the Many, Being and not-Being, the Same and the Other, Rest and Motion. It matters nothing that he should have followed Plato to the extent of co-ordinating five of these terms as supreme archetypal Ideas, immediately resulting from the self-consciousness of Nous, and themselves producing all other forms of existence. They are used, quite independently of that derivation, to explain the connexion of the various323 creative principles with one another. Nous is deduced from its first cause as Being from not-Being, as the Many from the One, as Difference from Identity, and as Motion from Rest.474 To explain the generation of Soul from Nous is a more difficult problem. The One had originally been defined as the antithetical cause of Nous, and therefore the latter could easily be accounted for by simply reversing the analytical process; whereas Nous had not been defined as the cause of Soul, but as the model whence her creative Ideas are derived. Soul, in fact, is not opposed to anything; she is the connecting link between sense and spirit. In this strait, Plotinus seems to think that the antithesis between Rest and Motion is the best fitted to express the nature of her descent from the higher principle; and on one occasion he illustrates the relation of his three divine substances to one another by the famous figure of a central point representing the One, a fixed circle round that point representing the Nous, and outside that, again, a revolving circle representing the Soul.475 Still, the different parts of the system are very awkwardly pieced together at this juncture; for the creative energy of the Nous has already been invoked to account for the Ideas or partial intelligences into which it spontaneously divides; and one does not understand how it can be simultaneously applied to the production of something that is not an Idea at all.