Learn / Glossary

Denying the antecedent

Inferring that a result cannot occur because one sufficient condition did not occur.

Published 04 August 2026Updated 04 August 2026

Denying the antecedent has the invalid form: if A, then B; not A; therefore not B. The argument overlooks other routes to B unless the original rule explicitly says A is necessary as well as sufficient.

Sources

Fallacies (Stanford Encyclopedia of Philosophy)

Stanford Encyclopedia of Philosophy / 2024 / Website

Canonical philosophical treatment of fallacy types.