Abstract

Descartes’s Cogito, “I am thinking, therefore I exist,” is perhaps the most famous assertion in the history of philosophy. Thirteen hundred years earlier, St. Augustine formulated a similar claim, arguing “if I am mistaken, I am.” Did St. Augustine anticipate Descartes? We show that Descartes’s dictum is a novel insight and less vulnerable to criticism than the claim of St. Augustine. Whereas Descartes searched for one true proposition on which he could base scientificknowledge, St. Augustine sought to refute the skeptics who had denied the possibility of knowledge. By a twist of irony, the skeptics and St. Augustine reached contradictory (ethical) conclusions based, however, on similar reasoning.