The Complete Aristotle (eng.)

affirmation finds its contrary in
a denial or in another affirmation; whether the proposition ‘every
man is just’ finds its contrary in the proposition ‘no man is
just’, or in the proposition ‘every man is unjust’. Take the
propositions ‘Callias is just’, ‘Callias is not just’, ‘Callias is
unjust’; we have to discover which of these form contraries.
    Now if the spoken word corresponds with the judgement of the
mind, and if, in thought, that judgement is the contrary of
another, which pronounces a contrary fact, in the way, for
instance, in which the judgement ‘every man is just’ pronounces a
contrary to that pronounced by the judgement ‘every man is unjust’,
the same must needs hold good with regard to spoken
affirmations.
    But if, in thought, it is not the judgement which pronounces a
contrary fact that is the contrary of another, then one affirmation
will not find its contrary in another, but rather in the
corresponding denial. We must therefore consider which true
judgement is the contrary of the false, that which forms the denial
of the false judgement or that which affirms the contrary fact.
    Let me illustrate. There is a true judgement concerning that
which is good, that it is good; another, a false judgement, that it
is not good; and a third, which is distinct, that it is bad. Which
of these two is contrary to the true? And if they are one and the
same, which mode of expression forms the contrary?
    It is an error to suppose that judgements are to be defined as
contrary in virtue of the fact that they have contrary subjects;
for the judgement concerning a good thing, that it is good, and
that concerning a bad thing, that it is bad, may be one and the
same, and whether they are so or not, they both represent the
truth. Yet the subjects here are contrary. But judgements are not
contrary because they have contrary subjects, but because they are
to the contrary effect.
    Now if we take the judgement that that which is good is good,
and another that it is not good, and if there are at the same time
other attributes, which do not and cannot belong to the good, we
must nevertheless refuse to treat as the contraries of the true
judgement those which opine that some other attribute subsists
which does not subsist, as also those that opine that some other
attribute does not subsist which does subsist, for both these
classes of judgement are of unlimited content.
    Those judgements must rather be termed contrary to the true
judgements, in which error is present. Now these judgements are
those which are concerned with the starting points of generation,
and generation is the passing from one extreme to its opposite;
therefore error is a like transition.
    Now that which is good is both good and not bad. The first
quality is part of its essence, the second accidental; for it is by
accident that it is not bad. But if that true judgement is most
really true, which concerns the subject’s intrinsic nature, then
that false judgement likewise is most really false, which concerns
its intrinsic nature. Now the judgement that that is good is not
good is a false judgement concerning its intrinsic nature, the
judgement that it is bad is one concerning that which is
accidental. Thus the judgement which denies the true judgement is
more really false than that which positively asserts the presence
of the contrary quality. But it is the man who forms that judgement
which is contrary to the true who is most thoroughly deceived, for
contraries are among the things which differ most widely within the
same class. If then of the two judgements one is contrary to the
true judgement, but that which is contradictory is the more truly
contrary, then the latter, it seems, is the real contrary. The
judgement that that which is good is bad is composite. For
presumably the man who forms that judgement must at the same time
understand that that which is good is not good.
    Further, the contradictory is either always the contrary or
never; therefore, if it must necessarily be so in all other cases,
our conclusion in the case just dealt with would seem to be
correct. Now where terms have no contrary, that judgement is false,
which forms the negative of the true; for instance, he who thinks a
man is not a man forms a false judgement. If then in these cases
the negative is the contrary, then the principle is universal in
its application.
    Again, the judgement that that which is not good is not good is
parallel with the