Ryan Wasserman

Assume that, even with a time machine, Tim does not have the ability to travel to the past and kill Grandfather. Why would that be? And what are the implications for traditional debates about freedom? We argue that there are at least two satisfactory explanations for why Tim cannot kill Grandfather. First, if an agent’s behavior at time _t_ is causally dependent on fact _F_, then the agent cannot perform an action (at _t_) that would require _F_ to have not obtained. Second, if an agent’s behavior at time _t_ is causally dependent on fact _F_, then the agent cannot perform an action (at _t_) that would prevent _F_ from obtaining. These two explanations have distinct upshots for more traditional debates over freedom. The first implies that causal determinism is incompatible with the ability to do otherwise and also raises questions about the traditional arguments for the incompatibility of divine foreknowledge and the ability to do otherwise; the second does neither. However, both explanations imply that the Molinist account of divine providence renders agents unable to do otherwise, at least in certain circumstances.

This is a paper about time travel and what it teaches us about freedom. I argue that cases of time travel bring out an important difference between two ways of thinking about “the past”—either in terms of time itself, or in terms of causation. This ambiguity naturally transfers over to our talk about things like fixity, determinism, and incompatibilism. Moreover, certain cases of time travel suggest that our freedom is not constrained by the temporal past _per se_, but by our own causal histories. This, in turn, raises a number of interesting questions about the formulation of incompatibilism and the broader debate over freedom.