This article interprets Madame de Lafayette’s La Princesse de Clèves as a response to Blaise Pascal’s arithmetic triangle. Pascal used the numbers of the triangle to determine how to divide fairly the stakes of an interrupted game of chance. He called his method “the geometry of chance,” and he touted it as an expansion of “the empire of reason” into formerly ungovernable territory. However, Pascal never applied the arithmetic triangle to games with more than two players, and the love triangle among the central characters in Lafayette’s novel implicitly ridicules this constraint. The frame around the present argument extends its significance beyond La Princesse de Clèves to the modern literary mechanisms whose origins critics have identified with it.