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Affirming the consequent

Inferring a condition from its result even though other conditions could produce the same result.

Published 04 August 2026Updated 04 August 2026

Affirming the consequent has the invalid form: if A, then B; B; therefore A. The rule says A is enough for B, not that A is the only route to B, so alternative explanations must remain open.

Sources

Fallacies (Stanford Encyclopedia of Philosophy)

Stanford Encyclopedia of Philosophy / 2024 / Website

Canonical philosophical treatment of fallacy types.