Paper 1 · Logical Reasoning
UGC NET June 2023 (15.06.2023) Shift-I
Which of the following statements are logically equivalent?
- All saints are materialists.
- No saints are non-materialists.
- All non-materialists are non-saints.
- No materialists are saints.
A2, 3 & 4 only
B1 & 3 only
C1 & 2 only
D1, 2 & 3 only ✓ Correct
Correct answer: (D) 1, 2 & 3 only — Statements 1, 2 and 3 are logically equivalent, so the answer is 1, 2 and 3.
Explanation
★Statements 1, 2 and 3 are logically equivalent, so the answer is 1, 2 and 3.
★All saints are materialists is the universal affirmative A proposition.
★Its obverse is no saints are non-materialists, which keeps the same meaning, matching statement 2.
★Its contrapositive is all non-materialists are non-saints, also equivalent, matching statement 3.
★So statements 1, 2 and 3 all say the same thing in different logical forms.
★No materialists are saints in statement 4 denies overlap the other way and is not equivalent.
★Obversion and contraposition preserve the truth of an A proposition, which is why the three agree.
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