In this critical edition, Leibniz submits his metaphysics of substance and form, concomitance and expression, freedom and necessity to the searching Socratic interrogation of Arnauld In this critical edition, Stephen Voss establishes the text of the magnificent Socratic correspondence between Gottfried Wilhelm Leibniz and Antoine Arnauld, provides an accurate English translation of the French text, and includes full apparatus helpful to student and scholar alike. The philosopher, physicist, and mathematician Leibniz presents the philosopher and theologian Arnauld with a unique new metaphysics and hones his ongoing thinking on the critical responses he receives. The result is a dialogue capable of illuminating metaphysical thought even now.