CONTRARY.—Aristotle defines contrary, «that which in the same genus differs most;» as in colour, white and black; in sensation, pleasure and pain; in morals, good and evil. Contrary, like contradictory, is applied both to Terms and Propositions. This relation to one another is different from that of contradictions, e.g., » Pleasure and pain are opposed to each other as contraries, not as contradictories, that is, the affirmation of the one implies the negation of the other, but the negation of the one does not infer the affirmation of the other; for there may be a third or intermediate state, which is neither one of pleasure nor one of pain, but one of indifference» (Hamilton, Metaph, lect. XLII. vol. II. p; 436). Of Propositions, the Universal Affirmative (A) and the Universal Negative (E) are opposed to one another as contraries, and of these both cannot be true, and both may be false. Thus, the affirmative of the one implies the negative of the other, but not vice versâ. Sub-contrary propositions are the particular affirmative (I) and the particular negative (0). Of these both may be true, and only one can be false.
