One of two opposite positions being affirmed, the other is denied.

Explanation

(English-origin maxim.) The affirmation of one of two contradictory propositions necessarily denies the other — a party cannot assert both sides of a contradiction.

Where this applies

• A defendant in a contract dispute claims the agreement was both valid and void at the same time — the court says affirming one position necessarily denies the other.
• A party argues that a deed was both properly executed and improperly executed simultaneously, and the court says these contradictory positions cannot coexist.
• A witness testifies that a signature is both authentic and forged, and the court rejects the testimony because affirming one necessarily denies the other.