Determinism, Counterfactuals, and the Possibility of Time Travel

Abstract

The Consequence argument is an argument from plausible premises–our lack of causal power over the laws and past–to an implausible conclusion: that if determinism is true, we are equally powerless with respect to the future. What the compatibilist needs is a theory of counterfactuals that preserves the links between counterfactuals, causation, and the natural laws in a way that supports our commonsense belief that we have the power to make a causal difference to the future but no such power with respect to the past. Lewis’s critique of the Consequence argument was based on his theory of counterfactuals and his analysis of causation as a counterfactual relation between particular events. He argued that, at a world that is deterministic in the way that ours might be, counterfactuals are temporally asymmetric in a way that matches the contingent temporal asymmetry of cauation. So it is not surprising, but only to be expected, that the past is causally closed while the future is causally open. If this worked, it would be just what the compatibilist needs. But it doesn’t work. There is an argument, due to Tooley and recently endorsed by Wasserman, that a fundamental feature of Lewis’s theory of counterfactuals is inconsistent with the metaphysical possibility of time travel and backwards causation. If this is right, then Lewis’s response to the Consequence argument fails. I endorse this conclusion, but argue that there is a better theory of counterfactuals–a theory that leaves open the metaphysical possibility of time travel to the past and backwards causation.