General Theory
-Prove that no valid syllogism in the second figure can have an affirmative conclusion.

Question

Quizplus · Accepted Answer

The Answer is The general form of a syllogism in the second figure is

P _ M

S _ M

S _ P

If the conclusion is affirmative, no premises may be negative (by rule 4 for valid syllogisms). So the premises must be either A or I propositions. But neither A nor I propositions distribute their predicates. Hence any syllogism in the second figure containing only A or I premises violates the rule (rule 1) requiring the middle term to be distributed at least once.

General Theory -Prove That No Valid Syllogism in the Second Figure Can