What is affirming the consequent?

Affirming the consequent is a logical fallacy whereby the arguer incorrectly concludes the cause (antecedent) because of the effect (consequent).

 It takes the form:

Premise 1:       If p then q

Premise 2:       q

Conclusion:     Therefore, p

For example,

          If it rains then the pavement will be wet.

          The pavement is wet.

          Therefore, it has rained.

This is formally invalid; that is, even if the premises are true, the conclusion does not necessarily follow. The pavement might indeed be wet because of rain; however, it might also be wet because of a burst water pipe, or because someone has been throwing water balloons etc.

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