Affirming the consequent
In propositional logic, affirming the consequent (also known as converse error, fallacy of the converse, or confusion of necessity and sufficiency) is a formal fallacy (or an invalid form of argument) that is committed when, in the context of an indicative conditional statement, it is stated that because the consequent is true, therefore the antecedent is true. It takes on the following form: If P, then Q. Q. Therefore, P. which may also be phrased as P → Q {\displaystyle P\rightarrow Q} (P implies Q) ∴ Q → P {\displaystyle \therefore Q\rightarrow P} (therefore, Q implies P) For example, it may be true that a broken lamp would cause a room to become dark.