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

by George Hastings McNair

The logical arrangement of syllogistic arguments is

1. Major premise.

2. Minor premise.

3. Conclusion.

Any proposition in a syllogism which answers the question “Why?” is a premise, whereas the conclusion follows “therefore”, or its equivalent either written or understood. If a conclusion is to be supplied, unite the two terms which are used but once in the premises, using the “minor premise term” as the subject. If a premise is to be supplied, unite the middle term with the “minor” to form the minor premise and with the “major” to form the major premise.

(3) Arguments which are regular, complete, and logically arranged, may be tested by symbolizing the mood and figure, underscoring the distributed terms, and then applying the general rules of the syllogism.

(4) Arguments with illogical premises may not be tested withimpunity till the faulty premises are made logical. The exclusive, an illogical proposition introduced by only, alone, none but, and the like, may be made logical by interchanging subject and predicate and calling the proposition an A. The individual proposition is one with a singular subject. In testing, individual propositions are classed as universal. Propositions introduced by “all-not” are usually given the significance of “some-not”. These are called partitive propositions, which in the testing, should be denominated “O’s”.

Inverted propositions when subjected to the test for validity must be converted simply and then classified. (Usually as A’s.)

(5) In supplying propositions which are taken for granted, the aim should be to make the argument valid, provided this can be done without violating the rules of logic, English, and common sense.

Ability to substitute equivalent words, phrases, or clauses is demanded of the student of logic, inasmuch as such substitution is frequently needed in the testing of arguments.