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physics to be other than they actually are (Incompatibility 23). Lewis objects to this assumption of van Inwagen’s argument, which claims that a person is unable to change the natural laws, by drawing upon his theory of possible worlds. Lewis believes that there exists a vast number of possible worlds, each of which is just as real and exists in the exact same sense as our actual world, such that everyone in his/her respective world views that world as the actual one. They are, however, separated spatiotemporally from each of the other possible worlds, such that there exist neither interactions nor causal relations between objects in different worlds. According to Lewis, “a possible world is a complete or total way things might have been, a complete or total way things might have gone” (Loux 193). This means that each person can only ever exist in one and the same world throughout his/her lifetime. There is such a thing, though, as an individual’s “counterparts.” Lewis explains the relationship between you and your counterparts as such: You are in the actual world and no other, but you have counterparts in several other worlds. Your counterparts resemble you closely in content and context in important respects. They resemble you more closely than do the other things in their worlds. But they are not really you. For each of them is in his own world, and only you are here in the actual world” (qtd. in Loux 197). The fact that we each have counterparts that exist in various possible worlds is one of the notions that leads Lewis to claim that we are able to do otherwise in each of our own actual worlds. He also claims that each person is determined partly by the laws that are specific to the actual world in which he/she lives. Lewis views determinism in terms of each possible world, and not a set of past events and universal laws as a whole that describe the set of all possible worlds.2 He argues that we are able to control natural laws, albeit in a very weak sense, and thereby uphold compatibilism. Lewis does not believe that we are able to “break a law,” but he does think that we are able to do something such that, if we did it, “a law would be broken,” referring to this law-breaking event as a “divergence miracle,” and it is in this weak sense that Lewis claims we are able to “control” natural laws (Free 31). This is his reasoning: Suppose in the actual world in which I live, I did not raise my hand. But if I had raised my hand, then a law would have been broken before that act, A, of raising my hand. Since we live in a deterministic world, the events that led up to my not raising my hand along with the natural laws determined that I keep my hand on the table. But if I had raised my hand, then the conjunction of the previous events and the natural laws would have to have been false before A occurred. Since Lewis claims that “a minor violation of laws counts against closeness less than does a difference in facts throughout the whole of the past,” (Beebee 237) then some law L, somewhere, would have been broken to enable me to raise my hand (Free 30-31). Lewis clarifies what he means by this type of miracle: When I say that a miracle takes place at w1, I mean that there is a violation of the laws of nature. But note that the violated laws are not laws of the same world where they are violated. That is impossible; whatever else a law may be, it is at least an exceptionless regularity. I am using ‘miracle’ to express a relation between different worlds. A miracle at w1, relative to w0, is a violation at w1 of the laws of w0, which are at best the almost-laws of w1. The laws of w1 itself, if such there be, do not enter into it (Counterfactual 468-9).
