Leibniz and the Metaphysics of Motion

Abstract

Th is essay develops an interpretation of Leibniz' theory of motion that strives to integrate his metaphysics of force with his doctrine of the equivalence of hypotheses, but which also supports a realist, as opposed to a fully ideal- ist, interpretation of his natural philosophy. Overall, the modern approaches to Leibniz' physics that rely on a fi xed spacetime backdrop, classical mechanical constructions, or absolute speed, will be revealed as defi cient, whereas a more adequate interpretation will be advanced that draws inspiration from an invari- antist conception of reality and recent non-classical theories of physics. Keywords: Leibniz, motion, matter, space, force, relativity, realism, idealism. Among recent trends in the history and philosophy of science, the at- tempts to interpret Leibniz' physics using the conceptual resources employed by contemporary theories of classical physics have achieved little, if any, suc- cess. In response to the obvious diffi culties associated with reconciling his al- leged commitment to relational motion with a conservation law that is quite inhospitable to relational motion, commentators have espoused various strat- egies for circumventing this obstacle, such as the use of reference frames in a spacetime structure congenial to relational motion, or the endorsement of absolute motion or speed, as Leibniz' preferred view. 1 Nearly all of the modern reconstructions, furthermore, attempt to reconstruct Leibniz' physics within the context of classical mechanics or classical gravitation theories, namely, by comparing Leibniz' conception of body, velocity, force, etc., against their