A Class Room Logic / Deductive and Inductive, with Special Application to the Science and Art of Teaching

by George Hastings McNair

(7) Hypothetical arguments may be tested by following this outline:

(1) Arrange logically.

(2) Determine antecedent and consequent.

(3) Apply hypothetical rule.

(4) Reduce to categorical form.

(5) Apply categorical rules.

(8) A disjunctive syllogism is one in which the major premise is a disjunctive proposition.

(9) The two kinds of disjunctives are those which “by affirming deny” and those which “by denying affirm.”

(10) In testing disjunctive arguments there are two rules involved: First, “The major premise must assert a logical disjunction.” This necessitates the two requisites “the alternatives must be mutually exclusive” and the “enumeration must be complete.” The two opinions relative to the nature of an alternative assertion are, first, if one is false, the other must be true and vice versa; and second, if one is false, the other must be true, but both may be true. The first is adopted in this discussion.

Second. The second rule involved is “When the minor premise affirms or denies one of the alternatives of a logical disjunctive the conclusion must deny or affirm all of the others.”