The Complete Aristotle (eng.)

for instance by those who make the unequal
matter for the equal, or the many matter for the one. But this also
is refuted in the same way; for the one matter which underlies any
pair of contraries is contrary to nothing. Further, all things,
except the one, will, on the view we are criticizing, partake of
evil; for the bad itself is one of the two elements. But the other
school does not treat the good and the bad even as principles; yet
in all things the good is in the highest degree a principle. The
school we first mentioned is right in saying that it is a
principle, but how the good is a principle they do not say-whether
as end or as mover or as form.
    Empedocles also has a paradoxical view; for he identifies the
good with love, but this is a principle both as mover (for it
brings things together) and as matter (for it is part of the
mixture). Now even if it happens that the same thing is a principle
both as matter and as mover, still the being, at least, of the two
is not the same. In which respect then is love a principle? It is
paradoxical also that strife should be imperishable; the nature of
his ‘evil’ is just strife.
    Anaxagoras makes the good a motive principle; for his ‘reason’
moves things. But it moves them for an end, which must be something
other than it, except according to our way of stating the case;
for, on our view, the medical art is in a sense health. It is
paradoxical also not to suppose a contrary to the good, i.e. to
reason. But all who speak of the contraries make no use of the
contraries, unless we bring their views into shape. And why some
things are perishable and others imperishable, no one tells us; for
they make all existing things out of the same principles. Further,
some make existing things out of the nonexistent; and others to
avoid the necessity of this make all things one.
    Further, why should there always be becoming, and what is the
cause of becoming?-this no one tells us. And those who suppose two
principles must suppose another, a superior principle, and so must
those who believe in the Forms; for why did things come to
participate, or why do they participate, in the Forms? And all
other thinkers are confronted by the necessary consequence that
there is something contrary to Wisdom, i.e. to the highest
knowledge; but we are not. For there is nothing contrary to that
which is primary; for all contraries have matter, and things that
have matter exist only potentially; and the ignorance which is
contrary to any knowledge leads to an object contrary to the object
of the knowledge; but what is primary has no contrary.
    Again, if besides sensible things no others exist, there will be
no first principle, no order, no becoming, no heavenly bodies, but
each principle will have a principle before it, as in the accounts
of the theologians and all the natural philosophers. But if the
Forms or the numbers are to exist, they will be causes of nothing;
or if not that, at least not of movement. Further, how is
extension, i.e. a continuum, to be produced out of unextended
parts? For number will not, either as mover or as form, produce a
continuum. But again there cannot be any contrary that is also
essentially a productive or moving principle; for it would be
possible for it not to be. Or at least its action would be
posterior to its potency. The world, then, would not be eternal.
But it is; one of these premisses, then, must be denied. And we
have said how this must be done. Further, in virtue of what the
numbers, or the soul and the body, or in general the form and the
thing, are one-of this no one tells us anything; nor can any one
tell, unless he says, as we do, that the mover makes them one. And
those who say mathematical number is first and go on to generate
one kind of substance after another and give different principles
for each, make the substance of the universe a mere series of
episodes (for one substance has no influence on another by its
existence or nonexistence), and they give us many governing
principles; but the world refuses to be governed badly.
‘The rule of many is not good; one ruler let there be.’

Book XIII
    Translated by W. D. Ross
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    div id="section141" class="section" title="1">
1
    We have stated what is the substance of sensible things, dealing
in the treatise on physics with matter, and later with the
substance which has actual existence. Now since our inquiry is
whether there is or is not besides the sensible substances any
which is immovable and