David Marshall Miller


Iowa State University

Descartes and His Critics on Conserved Rectilinear Motion

The modern principle of rectilinear inertia—uniform rectilinear motion is conserved—is often attributed to Descartes. But where in Descartes’s work is the modern principle found? I argue that the commonly accepted locus of attribution is misplaced. The origin of rectilinear inertia is not to be found in the mature metaphysics of the Principles of Philosophy, but rather in Descartes’s physical work, specifically in his Optics.