Pengyu He
Sun Yat-sen University
Non-reductive physicalism aims to reconcile mental causation with the causal closure of the physical domain. A prominent strategy appeals to weak overdetermination, according to which mental and physical causes jointly determine effects without the problematic independence characteristic of standard overdetermination. This paper argues that the strategy is not merely unsuccessful, but structurally unstable.
I articulate three minimal constraints on any adequate account of mental causation: (i) causal closure of the physical, (ii) non-redundancy of causes, and (iii) mind–body supervenience. I show that weak overdetermination cannot satisfy these constraints simultaneously. If the physical realizer is sufficient for the effect, the mental cause is rendered causally redundant; if it is not sufficient, causal closure is violated. Attempts to avoid this dilemma—such as sensitivity-based accounts or contrastivist approaches—either conflate cross-case generality with token-level causation or reduce causation to mere difference-making, thereby failing to secure genuine causal efficacy.
The upshot is a general negative result: weak overdetermination cannot provide a stable middle ground between reductionism and epiphenomenalism. More broadly, the paper suggests that any view that seeks to preserve mental causation while retaining both causal closure and supervenience faces a comparable instability.
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SOPhiA 2026 