not remain in themselves and by themselves? Why should they need to reproduce themselves in objects? There are, we know, white objects in the universe. Their existence, we are told, is explained by the Idea of whiteness? But why should the Idea of whiteness produce white things? It is itself the perfect whiteness. Why should it stir itself? Why should it not remain by itself, apart, sterile, in the world of Ideas, for all eternity? We cannot see. There is in the Ideas no necessity urging them towards reproduction of themselves, and this means that they possess no principle for the explanation of things. Nevertheless Plato has to make some attempt to meet the difficulty. And as the Ideas are themselves impotent to produce things, Plato, unable to solve the problem by reason, attempts to solve it by violence. He drags in the notion of God from nowhere in particular, and uses him as a _deus ex machina_. God fashions matter into the images of Ideas. The very fact that Plato is forced to introduce a creator shows that, in the Ideas themselves, there is no ground of explanation. Things ought to be explained by the Ideas themselves, {238} but as they are incapable of explaining anything, God is called upon to do their work for them. Thus Plato, faced with the problem of existence, practically deserts his theory of Ideas, and falls back upon a crude theism. Or if we say that the term God is not to be taken literally, and that Plato uses it merely as a figurative term for the Idea of Good, then this saves Plato from the charge of introducing a theism altogether inconsistent with his philosophy, but it brings us back to the old difficulty. For in this case, the existence of things must be explained by means of the Idea of the Good. But this Idea is just as impotent as the other Ideas.