THE RULES OF THE SYLLOGISM.
197. The Terms of the Syllogism.—A reasoning which consists of three propositions of the traditional categorical form, and which contains three and only three terms, is called a categorical syllogism.
Of the three terms contained in a categorical syllogism, two appear in the conclusion and also in one or other of the premisses, while the third appears in the premisses only. That which appears as the predicate of the conclusion, and in one of the premisses, is called the major term ; that which appears as the subject of the conclusion, and in one of the premisses, is called the minor term ;[306] and that which appears in both the premisses, but not in the conclusion (being that term by their relations to which the mutual relation of the two other terms is determined), is called the middle term.
[306] The major and minor terms are also sometimes called the extremes of the syllogism.
Thus, in the syllogism,—
| All M is P, | |
| All S is M, | |
| therefore, | All S is P ; |
S is the minor term, M the middle term, and P the major term.
286 These respective designations of the terms of a syllogism resulted from such a syllogism as that just given being regarded as typical. With the exception of the somewhat rare case in which the terms of a proposition are coextensive, the above syllogism may be represented by the following diagram. Here
clearly the major term is the largest in extent, and the minor the smallest, while the middle occupies an intermediate position.