If a person falls ill after consuming mushrooms, and concludes 'since I have digestive problems this morning, the mixed vegetable soup I had last night must have contained mushrooms', what is the fault, if any, in the above reasoning?

AThis is a valid argument

BAffirming the consequent ✓ Correct

CUnthoughtful generalization

DSelf-reliance fallacy

Correct answer: (B) Affirming the consequent

Explanation

The reasoning commits the formal error of affirming the consequent.

The hidden conditional is that if the soup had mushrooms, then digestive trouble would follow.

The person observes the consequent, the digestive trouble this morning.

From that they wrongly assert the antecedent, that the soup contained mushrooms.

Affirming a true consequent does not establish the antecedent, since other causes could produce the same effect.

This invalid move from consequent back to antecedent is the fallacy of affirming the consequent.

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