'not the same' is so predicated). It is predicated of all existing
things; for everything that is existent and one is by its very
nature either one or not one with anything else.
The other, then, and the same are thus opposed. But difference
is not the same as otherness. For the other and that which it is other
than need not be other in some definite respect (for everything that
is existent is either other or the same), but that which is
different is different from some particular thing in some particular
respect, so that there must be something identical whereby they
differ. And this identical thing is genus or species; for everything
that differs differs either in genus or in species, in genus if the
things have not their matter in common and are not generated out of
each other (i.e. if they belong to different figures of
predication), and in species if they have the same genus ('genus'
meaning that identical thing which is essentially predicated of both
the different things).
Contraries are different, and contrariety is a kind of difference.
That we are right in this supposition is shown by induction. For all
of these too are seen to be different; they are not merely other,
but some are other in genus, and others are in the same line of
predication, and therefore in the same genus, and the same in genus.
We have distinguished elsewhere what sort of things are the same or
other in genus.
Since things which differ may differ from one another more or
less, there is also a greatest difference, and this I call
contrariety. That contrariety is the greatest difference is made clear
by induction. For things which differ in genus have no way to one
another, but are too far distant and are not comparable; and for
things that differ in species the extremes from which generation takes
place are the contraries, and the distance between extremes-and
therefore that between the contraries-is the greatest.
But surely that which is greatest in each class is complete. For
that is greatest which cannot be exceeded, and that is complete beyond
which nothing can be found. For the complete difference marks the
end of a series (just as the other things which are called complete
are so called because they have attained an end), and beyond the end
there is nothing; for in everything it is the extreme and includes all
else, and therefore there is nothing beyond the end, and the
complete needs nothing further. From this, then, it is clear that
contrariety is complete difference; and as contraries are so called in
several senses, their modes of completeness will answer to the various
modes of contrariety which attach to the contraries.
This being so, it is clear that one thing have more than one
contrary (for neither can there be anything more extreme than the
extreme, nor can there be more than two extremes for the one
interval), and, to put the matter generally, this is clear if
contrariety is a difference, and if difference, and therefore also the
complete difference, must be between two things.
And the other commonly accepted definitions of contraries are also
necessarily true. For not only is (1) the complete difference the
greatest difference (for we can get no difference beyond it of
things differing either in genus or in species; for it has been
shown that there is no 'difference' between anything and the things
outside its genus, and among the things which differ in species the
complete difference is the greatest); but also (2) the things in the
same genus which differ most are contrary (for the complete difference
is the greatest difference between species of the same genus); and (3)
the things in the same receptive material which differ most are
contrary (for the matter is the same for contraries); and (4) of the
things which fall under the same faculty the most different are
contrary (for one science deals with one class of things, and in these
the complete difference is the greatest).