Tuesday, 13 March 2012
Conservation, Activity, and the Anti-Cartesian Argument of the Queries to Newton's Opticks
Katherine Dunlop, Department of Philosophy
12:05 pm, 817R Cathedral of Learning
Abstract: I examine the argument in Query 31 of Newton's Opticks for the necessity of "active principles". Newton considers bodies as possessing only the "passive principle" that is inertia. He argues, first, that a certain revolving system does not have the same quantity of motion in every phase, and secondly, that a body's motion is "always upon the Decay" whether it moves through a fluid medium or collides with another in vacuo. What makes this seemingly straightforward argument puzzling is that on Newton's view the dispositions conferred by vis inertiae are articulated by the three Laws of Motion, and therefore suffice for conservation of momentum. On my interpretation, the argument proceeds from premises that a Cartesian--but not necessarily Newton himself--must accept. It shows that Descartes's view that God conserves motion is untenable in light of Descartes's physical theory. This interpretation is supported by the use to which the argument is put by Newton's associates and followers. Newton and Descartes disagree on methodology and theology as well as physical theory: on Newton's view, God's involvement in the natural world is to be demonstrated through specific laws. Newton's remarks on comets illustrate how such a demonstration must go.