On Interpratation   

is white', 'no man is white' are meant. When, on the other hand, the

positive and negative propositions, though they have regard to a

universal, are yet not of universal character, they will not be

contrary, albeit the meaning intended is sometimes contrary. As

instances of propositions made with regard to a universal, but not

of universal character, we may take the 'propositions 'man is

white', 'man is not white'. 'Man' is a universal, but the

proposition is not made as of universal character; for the word

'every' does not make the subject a universal, but rather gives the

proposition a universal character. If, however, both predicate and

subject are distributed, the proposition thus constituted is

contrary to truth; no affirmation will, under such circumstances, be

true. The proposition 'every man is every animal' is an example of

this type.

An affirmation is opposed to a denial in the sense which I denote by

the term 'contradictory', when, while the subject remains the same,

the affirmation is of universal character and the denial is not. The

affirmation 'every man is white' is the contradictory of the denial

'not every man is white', or again, the proposition 'no man is

white' is the contradictory of the proposition 'some men are white'.

But propositions are opposed as contraries when both the affirmation

and the denial are universal, as in the sentences 'every man is

white', 'no man is white', 'every man is just', 'no man is just'.

We see that in a pair of this sort both propositions cannot be true,

but the contradictories of a pair of contraries can sometimes both

be true with reference to the same subject; for instance 'not every

man is white' and some men are white' are both true. Of such

corresponding positive and negative propositions as refer to

universals and have a universal character, one must be true and the

other false. This is the case also when the reference is to

individuals, as in the propositions 'Socrates is white', 'Socrates

is not white'.