syllogism
n. a form of deductive reasoning in which a categorial proposition (i.e., one taking the form all X are Y, no X are Y, some X are Y, or some X are not Y) is combined with a second proposition having one of its terms in common with the first to yield a third proposition (the conclusion). For example: All men are mortal; some men are tall; therefore some mortals are tall. Of the numerous possible combinations of terms, only 24 are formally valid. An example of an invalid syllogism would be Some women are tall; all mothers are women; therefore some mothers are tall. Although the conclusion is doubtless empirically correct, it cannot be deduced from these premises. —syllogistic
adj.