A collection of essays on the philosophy of Antoine Arnauld. Arnauld was a philosopher-theologian influenced by Augustine and Descartes. His subsequent influence on John Locke, among others, is well documented. He is best known for his work on the philosophy of mind and language, including his direct realist theory of perception. Additionally, he was the first critic to raise the 'Cartesian Circle' objection against Descartes' Meditations and he was a close associate of Blaise Pascal.