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Related to contrapositive: Proof by contradiction, Proof by contrapositive
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For example, establish by induction that courage is desirable and use deduction to then conclude that cowardice is undesirable (II 8, 113b30), or secure the contrapositive of an intended statement by induction, then use modus tollens to establish the intended claim (II 8, 113b17-25).
128) The contrapositive of "if X, then Y" is "if not Y, then not X.