Contraposition is a replacement rule in logic that allows us to negate both sides of a conditional statement and flip-flop their positioning. Thus, P => Q is equivalent to ~Q => ~P. Contraposition is an important tool to remember, because it is often easier to think about if-then statements when they are expressed in this flipped manner. You also should absolutely, positively understand it if you are taking logic games portion of the LSAT.

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