Physics   

entered into the mixture, and if separation took place, there would be
a 'white' or a 'healthy' which was nothing but white or healthy, i.e.
was not the predicate of a subject. So his 'Mind' is an absurd person
aiming at the impossible, if he is supposed to wish to separate them,
and it is impossible to do so, both in respect of quantity and of
quality- of quantity, because there is no minimum magnitude, and of
quality, because affections are inseparable.
Nor is Anaxagoras right about the coming to be of homogeneous bodies.
It is true there is a sense in which clay is divided into pieces of
clay, but there is another in which it is not. Water and air are, and
are generated 'from' each other, but not in the way in which bricks
come 'from' a house and again a house 'from' bricks; and it is better
to assume a smaller and finite number of principles, as Empedocles
does.
Part 5
All thinkers then agree in making the contraries principles, both
those who describe the All as one and unmoved (for even Parmenides
treats hot and cold as principles under the names of fire and earth)
and those too who use the rare and the dense. The same is true of
Democritus also, with his plenum and void, both of which exist, be
says, the one as being, the other as not-being. Again he speaks of
differences in position, shape, and order, and these are genera of
which the species are contraries, namely, of position, above and
below, before and behind; of shape, angular and angle-less, straight
and round.
It is plain then that they all in one way or another identify the
contraries with the principles. And with good reason. For first
principles must not be derived from one another nor from anything
else, while everything has to be derived from them. But these
conditions are fulfilled by the primary contraries, which are not
derived from anything else because they are primary, nor from each
other because they are contraries.
But we must see how this can be arrived at as a reasoned result, as
well as in the way just indicated.
Our first presupposition must be that in nature nothing acts on, or is
acted on by, any other thing at random, nor may anything come from
anything else, unless we mean that it does so in virtue of a
concomitant attribute. For how could 'white' come from 'musical',
unless 'musical' happened to be an attribute of the not-white or of
the black? No, 'white' comes from 'not-white'-and not from any
'not-white', but from black or some intermediate colour. Similarly,
'musical' comes to be from 'not-musical', but not from any thing other
than musical, but from 'unmusical' or any intermediate state there may
be.
Nor again do things pass into the first chance thing; 'white' does not
pass into 'musical' (except, it may be, in virtue of a concomitant
attribute), but into 'not-white'-and not into any chance thing which
is not white, but into black or an intermediate colour; 'musical'
passes into 'not-musical'-and not into any chance thing other than
musical, but into 'unmusical' or any intermediate state there may be.
The same holds of other things also: even things which are not simple
but complex follow the same principle, but the opposite state has not
received a name, so we fail to notice the fact. What is in tune must
come from what is not in tune, and vice versa; the tuned passes into
untunedness-and not into any untunedness, but into the corresponding
opposite. It does not matter whether we take attunement, order, or
composition for our illustration; the principle is obviously the same
in all, and in fact applies equally to the production of a house, a
statue, or any other complex. A house comes from certain things in a
certain state of separation instead of conjunction, a statue (or any
other thing that has been shaped) from shapelessness-each of these
objects being partly order and partly composition.
If then this is true, everything that comes to be or passes away from,
or passes into, its contrary or an intermediate state. But the