The Port-Royal Grammar (originally Grammaire générale et raisonnée contenant les fondemens de l'art de parler, expliqués d'une manière claire et naturelle, "General and Rational Grammar, containing the fundamentals of the art of speaking, explained in a clear and natural manner") was a pioneering work in the philosophy of language. Published in 1660 by Antoine Arnauld and Claude Lancelot, it was the linguistic counterpart to the Port-Royal Logic (1662), both named after the Jansenist monastery of Port-Royal-des-Champs where their authors worked. The Grammar was heavily influenced by the Regulae of René Descartes and it has been held up as an example par excellence of Cartesian linguistics by Noam Chomsky. The central argument of the Grammar is that grammar is simply mental processes, which are universal; therefore grammar is universal.
It has been translated into English and published by Jacques Rieux and Bernard E. Rollin under the title General and Rational Grammar: The Port-Royal Grammar (The Hague: Mouton, 1975).