Quantum Action and Substance Causation

Abstract

Aristotelian-Thomistic metaphysics defends a hylomorphic account of substance causation. Recent arguments have developed approaches informed by quantum mechanics (Koons 2021 and 2022, Simpson 2021 and 2023, Pruss 2018). While these arguments have responded to Jaegwon Kim’s critiques concerning overdetermination and causal closure, the ontological status of substantial form, especially as it applies to the category of “thermal substances,” remains an open question. In particular, do the forms of thermal substances (1) qualify as natural kinds, meeting a moderate requirement for naturalistic explanation, and (2) do they actualize the kinds of causal powers needed for substance causation in a way that avoids the event causalist’s critique of explanatory vacuity? This paper defends substance causation on both counts, by relying on a robust reading of Aquinas’s original account of substance causation and its distinction between corporeal and virtual contact. Far from problematizing these recent accounts, a robust Thomistic account in fact vindicates recent contemporary hylomorphic approaches, and even resolves some of the gaps that remain in a sound Aristotelian-Thomistic response to standard critiques concerning substance causation’s naturalistic status and explanatory power.