Abstract

The essay contains six chapters and argues that a rich notion of harmony plays a larger role in Leibniz's metaphysics, and in his philosophy as a whole, than was previously recognized. After some introductory remarks, chapter two lists Leibniz's expectations for a theory of substance and discusses some important methodological commitments. Chapter three leverages this material in describing Leibniz's rejection of Cartesian and atomist mechanistic philosophy. Chapter four presents the central argument for Leibniz's own theory of substance, the argument for monads, assembling a more clear and complete formulation than Leibniz provided. ;With such introductory material out of the way, chapter five demonstrates that the argument for monads requires an additional premise for validity: there is no reality without unity. This illuminates an additional dimension to monadic simplicity, namely, ontological simplicity. Given this, Leibniz's unity of substance can be understood in terms of two criteria, a simplicity criterion and a predicates criterion. Examining these criteria shows that substantial unity must involve the larger question of why a given substance must be as it is and develop as it does. The answer to this larger question involves harmony. ;Analogies drawn from musical harmony are used to show, given God's design goal of creating the best of all possible worlds, that the need for maximal harmony dictates the monadic structure of the universe, as well as the internal features of all monads. Further, harmony provides the mechanism for unity, for true unity depends upon a teleological harmony. Thus, harmony plays a role in unifying both the universe and the individual substances within. ;Finally, chapter six introduces and handles some objections. The question of why these functions of harmony have previously been overlooked is answered in terms of goals and source texts. An objection from solipsism is rejected because it misunderstands important elements of Leibniz's metaphysics. A Kantian objection is also rejected for two reasons: Kant did not understand Leibniz correctly in several respects, and the objection is question begging, insofar as it requires elements of Kant's metaphysics and epistemology, none of which could, or arguably should, Leibniz accept