In the 1680s, Gottfried Leibniz and Antoine Arnauld engaged in a philosophically rich correspondence. One issue they discuss is modal metaphysics – questions concerning necessity, possibility, and essence. While Arnauld's contributions to the correspondence are considered generally astute, his contributions on this issue have not always received a warm treatment. I argue that Arnauld's criticisms of Leibniz are sophisticated and that Arnauld offers his own Cartesian account in its place. In particular, I argue that Arnauld offers an account of possibility (...) that is actualist, modal actualist and essence-based. (shrink)