Contrapositive of conditional – UGC NET Question

The contrapositive of a conditional "if p, then q" is formed by negating both the antecedent and the consequent and reversing their positions, giving "if not q, then not p". In classical logic, a conditional and its contrapositive are always logically equivalent. This means they share the same truth table and stand or fall together. Hence the statement described is called the contrapositive.

Option A:
Option A, converse, yields "if q, then p" by swapping the antecedent and consequent without negating them. The converse is not necessarily equivalent to the original and thus does not match the pattern in the question.

Option B:
Option B, inverse, gives "if not p, then not q" by negating both parts but keeping their positions. Like the converse, the inverse is not generally equivalent to the original conditional. Therefore inverse is not the correct answer.

Option C:
Option C, biconditional, expresses "p if and only if q" and asserts both directions of implication in one statement. It is a different connective altogether and not merely a transformation of a single conditional.

Option D:
Option D is correct because contrapositive is the recognised name for the transformed conditional that is always logically equivalent to the original. This equivalence underlies many proof techniques.