applies to possession and privation. Now if Socrates exists, it
is not necessary that one should be true and the other false, for
when he is not yet able to acquire the power of vision, both are
false, as also if Socrates is altogether non-existent.

But in the case of affirmation and negation, whether the subject
exists or not, one is always false and the other true. For
manifestly, if Socrates exists, one of the two propositions
'Socrates is ill', 'Socrates is not ill', is true, and the other
false. This is likewise the case if he does not exist; for if he
does not exist, to say that he is ill is false, to say that he is
not ill is true. Thus it is in the case of those opposites only,
which are opposite in the sense in which the term is used with
reference to affirmation and negation, that the rule holds good,
that one of the pair must be true and the other false.

Part 11

That the contrary of a good is an evil is shown by induction: the
contrary of health is disease, of courage, cowardice, and so on.
But the contrary of an evil is sometimes a good, sometimes an
evil. For defect, which is an evil, has excess for its contrary,
this also being an evil, and the mean. which is a good, is
equally the contrary of the one and of the other. It is only in a
few cases, however, that we see instances of this: in most, the
contrary of an evil is a good.

In the case of contraries, it is not always necessary that if one
exists the other should also exist: for if all become healthy
there will be health and no disease, and again, if everything