rtainly relations with matter. But the first and
highest science has to do with that which is unmoved and apart from
matter; its function is with the eternal first causes of things. There
are therefore three modes of theoretical inquiry: the science of
physics, the science of mathematics, the science of God. For it is
clear that if the divine is anywhere, it must be in that form of
existence I have spoken of (_i.e._ in first causes). . . . If,
therefore, there be {181} any form of existence immovable, this we must
regard as prior, and the philosophy of this we must consider the first
philosophy, universal for the same reason that it is first. It deals
with existence as such, inquiring what it is and what are its
attributes as pure existence."

This is somewhat more technical than the language of Plato, but if we
compare it with what was said above (p. 142) we shall find an essential
identity. Yet Aristotle frequently impugns Plato's doctrine of ideas,
sometimes on the lines already [322] taken by Plato himself (above, p.
158), sometimes in other ways. Thus (_Met_. Z. 15, 16) he says: "That
which is _one_ cannot be in many places at one time, but that which is
common or general is in many places at one time. Hence it follows that
no universal exists apart from the individual things. But those who
hold the doctrine of ideas, on one side are right, viz. in maintaining
their separate existence, if they are to be substances or existences at
all. On the other side they are wrong, because by the idea or form
which they maintain to be separate they mean the one attribute
predicable of many things. The reason why they do this is because they
cannot indicate what these supposed imperishable essences are, apart
from the individual substances which are the objects of perception.
The result is that they simply represent them under the same forms as
{182} those of the perishable objects of sensation which are familiar
to our senses, with the addition of a phrase--_i.e._ they say 'man as
such,' 'horse as such,' or 'the absolute man,' 'the absolute horse.'"

Aristotle here makes a point against Plato and his school, inasmuch as,
starting from the assumption that of the world of sense there could be
no knowledge, no apprehension fixed or certain, and setting over
against this a world of general forms which were fixed and certain,
they had nothing with which to fill this second supposed world except
the data of sense as foun