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

by George Hastings McNair

(8) Inverted Propositions.

The poet often employs the inverted proposition, illustrated by the following: “Blessed are the merciful;” “Great is this man of war.” An interchanging of subject and predicate makes these poetical constructions logical; e. g., “All the merciful are blessed;” “This man of war is great.”

NOTE.—The student should not be misled by the relative clause. Often it may be interpreted as a part of thepredicate rather than the subject. To wit: “No man is a friend who betrays a confidence”; clearly the logical subject is no man who betrays a confidence.

7. PROPOSITIONS WHICH ARE NOT NECESSARILY ILLOGICAL.

(1) Analytic and Synthetic Propositions.

An analytic proposition is one in which the predicate gives information already implied in the subject. Thus, “Fire burns,” “Water is wet,” “A triangle has three angles” are analytic propositions because the predicates do not give added information to one who has any conception of the subjects. Because the attribute mentioned by the predicate is an essential one, analytic propositions are sometimes termed essential propositions. Other names for the same kind of proposition are verbal and explicative.

A synthetic proposition is one in which the predicate gives information not necessarily implied in the subject. “Fire protects men from the wild animal.” “A cubic foot of water weighs 62¹⁄₂ lbs.” “The sum of the interior angles of a triangle is equal to two right angles.” These are synthetic because a common conception of the meaning of the subject would not need to include the information given by the predicate. Other names for synthetic propositions are accidental, real and ampliative.

The distinction between analytic and synthetic propositions is not so clear as would on first thought appear. “Fire burns” might give added information to the child or savage who knows only of the light emitted by fire.To them, then, the proposition would be synthetic. The distinction must be based upon the assumption that the same words mean about the same thing to people in general.

This analytic-synthetic division of propositions finds a significance in the domain of philosophy. To the logician the distinction is of slight importance save in the so-called verbal disputes, viz.: disputes which turn on the meaning of words.

(2) Modal and Pure Propositions.