Definition:A Fortiori

Definition
A fortiori knowledge arises from stronger facts already established.

For example, in:


 * I am too old for this game; therefore, my father is also too old.

the knowledge:


 * My father is too old for this game.

arises a fortiori from the stronger knowledge that:


 * I am too old for this game.

An a fortiori argument is most commonly used by applying a general fact in a particular case.