Friday, January 9, 2009

Possible Girls

People have occasionally asked to see some of my professional work. So today I give you my wackiest published paper: Possible Girls. It explains how one famous theory about the truth of counterfactual statements implies that you can have a girlfriend (or boyfriend) who lives in another universe.

I should give some background. One of the big philosophical mysteries that philosophers try to figure out concerns counterfactual claims, also called modal claims. For example:
"If the Democrats had nominated Sharpton, they would've lost."
"If I hadn't worn any clothes to school, I wouldn't have graduated."

Most philosophers think that for a statement to be true, it has to accurately describe some part of reality. So the question is, what part of reality is being described by these statements? In reality, the Democrats didn't nominate Sharpton and I wore clothes to school. We want to say that the above counterfactual statements are true, but it seems that we can't do this unless there's some aspect of reality that they accurately describe. Lots of metaphysicians have theories about what this aspect of reality is. Some of these theories involve nonphysical entities ("abstract objects") that serve the function of making modal claims true. Other philosophers don't believe in nonphysical stuff, so they don't like those theories.

David Lewis had a crazy but interesting suggestion. According to Lewis, there are an infinite number of universes ("possible worlds") out there, one for each possible way the world could be. These universes are disconnected from each other in space and time, and set up so that nothing in one universe can cause events in another universe. Relations between these possible worlds are the stuff that our counterfactual claims were supposed to accurately describe. According to him, here's what makes "If the Democrats had nominated Sharpton, they still would've lost" true: Consider the closest possible world (that is, the universe most like ours) where the Democrats nominate Sharpton. Do they lose in that universe? If so, the counterfactual statement is true. If they win, it's false.

All the other universes, according to Lewis, are real in just the same way as ours is real. They're made of physical stuff just like our universe is, so you don't have to believe in any nonphysical stuff to believe in them. Since there's one of these worlds for each possibility, there are an enormous number of real people out there. Some of them are girls who are thinking of boys from other universes. Starting from there, I show how you can get a one-to-one relationship with someone from another universe. I deal with a bunch of problems -- for example, how can you make sure that your otherworldly beloved is interested in you and not the person just like you from the next universe? (It involves your beloved being immortal and using her immortality to sing out an exhaustive description of your universe.)

This paper was accepted by Pacific Philosophical Quarterly, which is actually a respectable journal. The referee said that it made him laugh out loud several times. It's only eleven pages and I think it's fairly accessible. Feel free to ask any questions you have in comments, and tell me if there are any problems downloading the paper.
Post a Comment