 On February 11, 1686, while the controversy between Arnauld and Malebranche was at a peak of intensity, Leibniz wrote to Landgrave Ernst von Hessen-Rheinfels, asking that the Landgrave send Arnauld a summary of “a short discourse” on “questions of grace, the concourse of God and creatures, the nature of miracles, the cause of sin and the origin of evil, the immortality of the soul, ideas, etc.” (The Leibniz-Arnauld Correspondence, Die Philosophischen Schriften von Leibniz, herausgegeben von K. I. Gerhardt, Vol. 2, hereinafter LA, 11). The ensuing correspondence occurred at a crucial point in the development of Leibniz’s philosophy. The Discourse on Metaphysics, the final version of the short discourse, marks the beginning of Leibniz’s mature metaphysics, and it shows the influence of the correspondence with Arnauld.