OPPOSITION. In logic, the name applied to express the relation bet AN veil propo•it b Ins which have the same subject and the same predicate, but which differ in quality or in quantity. or in both. Thus "All cows ruminate" and cows ruminate" stand in opposition or are opposites, because they have the same terms ('cows' and 'ruminate') but differ in quantity. If opposites differ /nay in quantity. the universal proposition is called the subaltern and the particular the subalternate. When the opposites diger only in quality and are both universal, they are said to Le contraries: if they are both particular and differ only in quantity, they are said to be sub contraries. If the opposites differ in both quan tity and quality, they are said to be contradic tory. These relations arc generally represented graphically in the so-called 'square of opposi tion,' in which the symbols A, E. 1. O. stand for the four mutually opposing propositions. See Loc te.
From this square probably arises the expres sion 'squarely contradictory.' An 'immediate in ference by opposition' is made when from the klIONVII or granted truth or falsity of any prop osition, the truth or falsity of its opposites is in ferred. Thus, if A be true, E and O are false and 1 is true. If E be true, A and I are false and 0 is true. If I be true, E is false, and either—nut both—A or 0 is true; which is true cannot be inferred from the premise. If 0 be true. A is false, and either—not both—E or I is true; which is true cannot be inferred from the premise. On the other hand, if A he false, O is true. and either—not both—I or E is true; which is true cannot be inferred from the premise. If E be false. I is true, and either—not both—A or 0 is true; which is true cannot he inferred from the premise. If 1 be false, E and 0 are true, and A is false. If 0 be false. A and I are true and E is false.