Denying the Antecedent

If you are Canadian, then you can stay in Spain for 90 days. You aren’t Canadian. Therefore, you can’t stay in Spain for 90 days.

Denying the antecedent takes this form:
If P, then Q.
Not P.
Therefore, not Q.

In the previous example,
P: You are Canadian.
Q: You can stay in Spain for 90 days.

It is a fallacy because the first premise doesn’t say that only Canadians can stay in Spain for 90 days.

This can be tricky because it looks similar to modus tollens (denying the consequent), a valid argument form:

If P, then Q.
Not Q.
Therefore, not P.

Example:
If you are Canadian, then you can stay in Spain for 90 days. You can’t stay in Spain for 90 days, so you must not be Canadian. (valid)

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