hysical existence, seems doubtful.

Aristotle's metaphysical theory grows naturally out of his polemic
against Plato's theory of Ideas, because his own system was in effect
simply an attempt to overcome the defects which he found in Plato. The
main heads of this polemic are the following:--

(1) Plato's Ideas do not explain the existence of things. To explain
why the world is here is after all the main problem of philosophy, and
Plato's theory fails to do this. Even admitting that, say, the Idea of
whiteness exists, we cannot see how it produces white objects.

(2) Plato has not explained the relation of Ideas to things. Things,
we are told, are "copies" of Ideas, and "participate" in them. But how
are we to understand this "participation"? In using such phrases, says
Aristotle, Plato is giving no real account of the relationship, but is
merely "uttering poetic metaphors."

(3) Even if the existence of things is explained by the Ideas, their
motion is not. Suppose that the Idea of whiteness produces white
things, the Idea of beauty beautiful things, and so on, yet, since the
Ideas themselves are immutable and motionless, so will be the world
which is their copy. Thus the universe would be {263} absolutely
static, like Coleridge's "painted ship upon a painted ocean." But the
world, on the contrary, is a world of change, motion, life, becoming.
Plato makes no attempt to explain the unceasing becoming of things.
Even if the Idea of whiteness explains white objects, yet why do these
objects arise, develop, decay, and cease to exist? To explain this
there must be some principle of motion in the Ideas themselves. But
there is not. They are immovable and lifeless.

(4) The world consists of a multitude of things, and it is the
business of philosophy to explain why they exist. By way of
explanation Plato merely assumes the existence of another multitude of
things, the Ideas. But the only effect of this is to double the number
of things to be explained. How does it help thus to duplicate
everything? And Aristotle likens Plato to a man who, being unable to
count with a small number, fancies that, if he doubles the number, he
will find it easier to count.

(5) The Ideas are supposed to be non-sensuous, but they are, in fact,
sensuous. Plato thought that a non-sensuous principle must be sought
in order to explain the world of sense. But not being able to find any
such principle, he merely took the objects of sense over again