Duhaime's Law Dictionary

A fortiori Definition:

Latin: with all the more force.

A term of logic often used in law; meaning:

  • By even greater force of logic;
  • So much the more;
  • Even more likely; or
  • With even more certainty....

From John Trayner's 1861 dictionary:

"A fortiori: By a stronger argument; so much the more."

For example:

"If conduct does not constitute a civil wrong, a fortiori it cannot be a criminal wrong."

A proposition that is true because of another inclusive statement.

The Oxford Dictionary of Latin Words and Phrases:

"A fortiori: by a stronger reason, all the more."

Note these words of the Ontario Court of Appeal in Gallagher v Southam:

"We are of the opinion that the order ... is an interlocutory order and a fortiori the order refusing leave to appeal therefrom is not a final order in the sense of an order determining the lis between the parties...."


  • Gallagher v. Southam Inc., 1994 CanLII 777
  • Mayrand, A., Dictionnaire de Maximes et Locutions Latines Utilisées en Droit, 4th Ed. (Montreal: Editions Yvon Blais, 2006), page 33-34
  • Morwood, James, A Dictionary of Latin Words and Phrases (Oxford: Oxford University Press, 1998), page 11.
  • Trayner, John, Latin Phrases and Maxims Collected From the Institutional and Other Writers on Scotch Law with Translations and Illustrations (Edinburgh: William Paterson, 1861)

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