David Lewis's counterfactual arrow of time

David Lewis (1979) has argued that according to his possible worlds analysis of counterfactuals, "backtracking" counterfactuals of the form "If event A were to happen at tA, then event B would happen at tB" where tB precedes tA, are usually false if B does not actually happen at tB. On the other hand, there are plenty of such counterfactuals true with tA preceding tB; for instance it is true that were I to drop the glass now, it would hit the ground at some point in the future, even if in fact it does not do so. Assuming some contingent facts about the arrangement and laws of our universe, this time-reversal asymmetry, Lewis claims, follows from a possible worlds analysis of counterfactuals despite the fact that this analysis of counterfactuals is entirely time symmetric. Lewis argues, further, that this asymmetry gives meaning to the common notion of the future as "open" and the past as "closed", even if determinism both of the future by the past and of the past by the future is true, which for the purposes of the analysis he assumes it to be and in which assumption I will follow him in this paper. With Lewis, and also contrary to my own views, I will assume physicalism. Much of the argument of Lewis's (1979) paper is a reply to an objection that had been raised by Fine and others against his analysis of counterfactuals. I shall argue that Lewis's reply succeeds in some interesting special cases but fails in others to demonstrate the asymmetry he seeks. But even more seriously, I shall show that the asymmetry Lewis finds, if there actually is one to be found there, is grounded in the fact that there is a time-reversal asymmetric preselection in the kinds of events that figure as antecedents of ordinary language counterfactuals. We do not in practice ask: "What would happen if p held?" for every proposition p, but only for some. I argue that this preselection of some antecedents of counterfactuals but not others in everyday counterfactuals is based in part on the commonsensical notion that generally it is past events that are the causes of future