act, copies of Ideas come into
existence. There must be a reason for it, and this reason it is the
business of philosophy to explain. This reason, too, must exist in the
nature of the Ideas themselves, and not outside them. There must be,
in the very nature of the Ideas, some inner necessity which forces
them to reproduce themselves in things. This is what we {237} mean by
saying that the Ideas are a sufficient explanation of the existence of
things. But there is in Plato's Ideas no such necessity. The Ideas are
defined as being the sole reality. They have already all reality in
themselves. They are self-sufficient. They lack nothing. It is not
necessary for them further to realize their being in the concrete
manifestation of things, because they, as wholly real, need no
realization. Why, then, should they not remain for ever simply as they
are? Why should they go out of themselves into things? Why should they
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 c