Transposition (logic)
In propositional logic, transposition is a valid rule of replacement that permits one to switch the antecedent with the consequent of a conditional statement in a logical proof if they are also both negated. It is the inference from the truth of "A implies B" the truth of "Not-B implies not-A", and conversely. It is very closely related to the rule of inference modus tollens. It is the rule that:
- (P → Q) (¬ Q → ¬ P)
Where "" is a metalogical symbol representing "can be replaced in a proof with."
Read more about Transposition (logic): Formal Notation, Transposition in Mathematical Logic, Proof