A lively renewal of interest in Leibniz studies over the past fifteen years has witnessed the publication of many important monographs touching on Leibniz's metaphysics. The scope and tenor of these books is varied. Happily, Leibniz left plenty to go around – plenty enough to attract philosophers and historians of the early modern period, possessed of various temperaments and interests and talents, with a rich body of early writings, stretches of correspondence or reaction to a contemporary, sustained discussion of particular philosophical topics, broader thematic concerns, and so on.

This book – predictably enough, given our own temperaments and interests – has rather focused historical and philosophical aims. To understand Leibniz's metaphysics is, in some measure, to understand the historical ancestry of issues drawing his attention. Leibniz inherited a cluster of concerns about individuation that were prominent in the scholastic period; in his lifetime, he both shaped and refigured many of these concerns, and provided what he took to be a defensible treatment of them. Our historical objective is to gain some measure of appreciation for how Leibniz's views on substance and individuation emerge in the context of certain scholastic themes, and to secure a better understanding of those themes and their place in Leibniz's overall system.

Most of the themes are there already in Aristotle, bequeathed to the medievals as a metaphysic of primary substance. Aristotle, too, left plenty to go around.