Beeckman, Descartes and the force of motion RICHARD ARTHUR DEPARTMENT OF PHILOSOPHY MCMASTER UNIVERSITY HAMILTON, ONTARIO L8S 4K1 CANADA. E-mail:
[email protected] Abstract In this reassessment of Descartes’ debt to his mentor Isaac Beeckman, I argue that they share the same basic conception of motion: the force of a body's motion—understood as the force of persisting in that motion, shorn of any connotations of internal cause—is conserved through God's direct action, is proportional to the speed and magnitude of the body, and is gained or lost only through collisions. I contend that this constitutes a fully coherent ontology of motion, original with Beeckman and consistent with his atomism, which, notwithstanding Descartes' own profoundly original contributions to the theory of motion, is basic to all his further work in natural philosophy. Beeckman, Descartes and the force of motion 2 1. INTRODUCTION: DESCARTES’ CASTIGATION OF BEECKMAN In October 1629 René Descartes reacted with scorn and indignation to suggestions that he might have learned anything from his good friend Isaac Beeckman during their enthusiastic collaboration in Breda in 1618-19.1 Relations deteriorated, and a year later, in October 1630, Descartes wrote a long and vituperative letter to Beeckman that was clearly intended to be psychologically crushing, in which he scathingly disavowed any influence from Beeckman whatever.2 This has been interpreted by Klaas van Berkel as an attempt by Descartes, and a successful one too, to discourage Beeckman from his intention to