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Compare with valid argument.
*Jack is wearing his blue suit.
*Jack is wearing his blue suit.
*Therefore, Jack is meeting an important client today.
*Therefore, Jack is meeting an important client today.
Affirming the consequent is fallacious because the initial premise does not rule out situations in which ''Q'' could be true even without ''P.'' In other words, in formal logic, as in general speech, "if" does not mean "only if" or "if and only if." In the example given above, even if the first premise is invariably true, Jack could decide to wear his blue suit on other days.
Affirming the consequent is fallacious because the initial premise does not rule out situations in which ''Q'' could be true even without ''P.'' In other words, in formal logic, as in general speech, "if" does not mean "only if" or "if and only if." In the example given above, even if the first premise is invariably true, Jack could decide to wear his blue suit on other days. Compare the following argument, which, while superficially similar, is valid:
*If Jack is meeting an important client today, ''and not otherwise,'' he will wear his blue suit.
*Jack is wearing his blue suit.
*Therefore, Jack is meeting an important client today.
==Denying the ancecedent==
==Denying the ancecedent==
'''Denying the antecedent''' is a variant that takes the following form:
'''Denying the antecedent''' is a variant that takes the following form: