“If it rains, then the drought will end. The drought has ended. Therefore, it rained”. Which kind of fallacy does this commit?
Deductive fallacy
The argument has the form: If P then Q. Q is true. Therefore P. Here P = it rains and Q = the drought ends. This is the classic pattern of affirming the consequent.
A valid deduction (modus ponens) would affirm the antecedent: If P then Q, P is true, therefore Q. The given argument instead affirms the consequent (Q) and concludes the antecedent (P), which is an invalid form of deductive inference. The drought could have ended for many other reasons (irrigation, a river diversion, snow-melt), so the truth of the conclusion does not follow necessarily from the premises. Because the error lies in the structure of a deductive form that claims necessity but does not have it, it is a Deductive fallacy.
It is not an inductive fallacy (which concerns weak generalisation from evidence) or an abductive fallacy (faulty inference to the best explanation); those are non-deductive reasoning patterns. It is broadly an informal error too, but the precise and intended description of a mis-formed conditional inference is a deductive fallacy.
Correct answer: Deductive fallacy
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