In the study of the origins and development of French eighteenth century thought, the importance of Isaac de la Peyrère has been strangely overlooked. I say “strangely ”advisedly since not only was La Peyrère a person of some prominence in his day, but through his works, was one of the first to disseminate certain critical arguments which were to prove popular with deists in both France and England, and which find their highest degree of success in Voltaire's Essai sur les mœurs, La Bible enfin expliquée, and the Dictionnaire philosophique. Accordingly it is the purpose of this article to investigate La Peyrère's place among his contemporaries, the subsequent fortune of his ideas, and to attempt to evaluate his importance in the formation and development of critical deism in both France and England.