On Temporal and Causal Asymmetry

I argue that current physics does not support the claim that there is no microphysical causation. In the spirit of Russell’s (1912) ‘On the notion of cause’, many contemporary metaphysicians endorse the Russellian argument that because fundamental physics does not support a direction of time, and therefore that unidirectional causal relations cannot be found among the universe’s microphysical constituents, there is no microphysical causation. In this thesis, I critically assess this argument. I agree with Russellians about what time is like; I argue that given relativity and the time symmetry of the laws, we should think that our universe contains a four-dimensional spacetime manifold in which time lacks a primitive direction. I further agree with Russellians that, in general, we do not find unidirectional causal relations among microphysical phenomena. But I disagree with Russellians about what causation is like: I argue that causation is not always unidirectional on the basis of a case that we would ordinarily judge as causal, despite the dependence relations involved being bidirectional. Therefore, the bidirectionality of microphysical dependence relations should not motivate us to reject microphysical causation. Furthermore, we have independent reasons to think that there is microphysical causation; for example, Ney (2016) argues that a rejection of microphysical causation undermines the causal closure argument for physicalism. Therefore, we should think that causal relations can be bidirectional, and that there are causal relations among microphysical phenomena. Finally, I consider how one can give an account of causation that captures microphysical causal explanations while still allowing that there is genuine causal asymmetry at the level of macrophysics. Such an account is preferable for those (e.g. Farr 2022) who reject a primitive direction of time, because there is a question about how those who reject primitive temporal direction can account for the explanatory asymmetry that holds between the initial state of the universe and the final state of the universe (where the initial state is taken to explain the final state and not vice versa), and the best answers to this question appeal to causal asymmetries in macrophysics.