This text features Leibniz's own accounts of his work and comprises critical and historical notes and essays. An informative Introduction leads to the "postscript" to Leibniz's 1703 letter to James Bernoulli, his "Historia et Origio Calculi Differentialis," and manuscripts of the period 1673-77. Essays by C. I. Gerhardt follow, along with additional letters and manuscripts by Leibniz.