Closure Principles and the Laws of Conservation of Energy and Momentum

Abstract

The conservation laws do not establish the central premise within the argument from causal overdetermination - the causal completeness of the physical domain. Contrary to David Papineau (2000 and 2002), this is true even if there is no non-physical energy. The combination of the conservation laws with the claim that there is no non-physical energy would establish the causal completeness principle only if, at the very least, two further causal claims were accepted. First, the claim that the only way that something non-physical could affect a physical system is by (1) affecting the amount of energy or momentum within it, or (2) redistributing the energy and momentum within it. Second, the claim that redistribution of energy and momentum cannot be brought about without supplying energy or momentum. Both of these claims, however, are exceedingly difficult to defend in the context of the argument. Despite the importance of the principle of the causal completeness of the physical domain to physicalism, rigorous argument for it is hard to find - presumably because it is assumed to be an uncontentious claim that is supported by physics and that therefore requires little further defence from those in the mental causation debate. But how, exactly, is this principle supported by physics? One might presume that an answer to this question is to be found in the laws of conservation of energy and momentum - a cornerstone of contemporary physics. The thought that interactive dualism clashes with the conservation laws dates back to early criticisms of Descartes's theory of psychophysical causation, and is still popular in today's mental causation debate. 1 As Dennett writes: the principle of the conservation of energy is apparently violated by dualism. This confrontation between quite standard physics and dualism has been endlessly dis- cussed since Descartes' own day, and is widely regarded as the inescapable and fatal flaw of dualism (1991, 35). It is therefore perhaps unsurprising that it is these laws from which some assume the completeness principle ultimately to gain its support.