But when we observe that distinction it allows us to explain the real facts about possibility. Similarly, Lewis argues, we are inclined to be insensitive to the distinction between all that exists in our world and all that exists, overall. Accordingly, we would have been insensitive to the distinction between all that exists on our planet and all that exists, overall. At one time we may have thought that ours was the only planet. And, according to Lewis, that is a restricting thought: it is a thought about what exists locally – like saying that something exists in our country, or on our planet. Lewis thinks that when we say that something actually exists, we are saying that it exists in our world (our universe). Lewis’s conception of what there is may be extraordinary, or even shocking, but it is not arbitrary. The reader will note that for Lewis’s view to be consistent he must have been thinking that what actually exists is only a part of what exists overall. For there is an extended argument in support of it – in sum: genuine modal realism (as he calls his view) makes much better sense of a great deal of what we hold true than does the alternative (common-sense, conservative) conception that correlates existence with what is actual rather than with what is possible. For there is a governing theoretical principle here: it is that everything that could possibly exist does exist. We have no reason to believe that there are real facts about possibility because: (i) only science could tell us that there are, and (ii) it doesn’t. My response is that (b) is moot because we have no reason to believe that (a) is true. What is driving all this is a pair of thoughts: (a) there are real facts about what is possible and (b) these facts consist in the real existence of things in other possible worlds. And just as there exists a universe that conforms to special relativity, so there exists a universe that conforms to Newton’s laws. Just as brains exist so do the immaterial minds that Descartes thought were associated with them.

But our best scientific theories suggest that there are no real facts about what’s possible, and therefore possible worlds aren’t real, argues John Divers.ĭavid Lewis (in)famously argued that just about everything you can think of really exists. In trying to make sense of the way we talk about possibility, David Lewis argued that everything that could possibly exist does exist, in some possible world.

David lewis philosopher