The Principle of Least Action and Teleological Explanation in Physics

David Glick (University of California, Davis)

Variational principles present a prima facie challenge to the usual mode of causal explanation in physics. Historically, one such principle—the Principle of Least Action (PLA)—has been influential as a potential example of the (re-)introduction of teleology into physics. A contemporary response rests on the derivation of PLA as a limiting case from the Feynman Path Integral (FPI) approach to quantum field theory. If PLA can be derived from FPI, so the story goes, and the latter is non-teleological, then any apparent introduction of teleology by PLA is avoided. In this talk, I push back against this line of thought: the derivation of PLA from FPI as a limiting case does not undermine PLA as an autonomous explanatory principle. This means that it remains as an interesting case of non-causal explanation.