Which of the following statements are logically equivalent?

1.Some physicists are outstanding professors

2.Some physicists are not non-outstanding professors

3.No outstanding professors are physicists

4.Some non-outstanding professors are not non-physicists

A1, 2 & 4 only

B1 & 2 only ✓ Correct

C2 & 4 only

D1 & 3 only

Correct answer: (B) 1 & 2 only

Explanation

Statements 1 and 2 are logically equivalent.

Statement 1 "Some physicists are outstanding professors" is an I proposition.

Obversion changes quality and negates the predicate.

An I becomes O, "Some physicists are not non-outstanding professors", which is 2.

Statements 3 and 4 alter the terms and do not carry the same meaning.

Obversion is what binds statements 1 and 2.

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