It's Valentine's Day, the day when greeting card companies and Hollywood and the record studios decided that people in relationships ought to be stressed and single people ought to be miserable. It's pretty cool. But if you're in the singles camp, you're in luck. While you may not think you have a boyfriend/girlfriend/whatever, there's a chance that you in fact do -- and they're awesome.

At least that's what Neil Sinhababu says. Neil — who, coincidentally, was a frequent guest-blogger for the original Ezra Klein blog — is a philosopher at the National University of Singapore. His Facebook relationship status currently says "it's complicated" between him and Modal Realism. That's the theory, made famous by the late, great Princeton philosopher David Kellogg Lewis in his book On the Plurality of Worlds, that every possible world — that is, every possible state of affairs that could theoretically come into being — is equally real to the world we're all living in today.

No, seriously. Lewis believed that there are parallel worlds, just as physical and real as our own, in which Hitler won World War II, JFK wasn't assassinated, and Marco Rubio didn't reach for a water bottle during his State of the Union response. For each case, in fact, there are probably trillions of universes. There is a Hitler-wins universe where I had a donut for breakfast and Hitler-wins universe where I had a banana. Each, Lewis insisted, are as real as the world we inhabit right now.

To most people, that view sounds obviously insane. "Hitler didn't win World War II, either in this world or in any real world!" we want to say. But there's a problem with denying this. With some important exceptions, most philosophers believe statements are true or false depending on whether or not they describe the real world accurately. Makes sense right?

The trouble arises when we say things like, "If John McCain had won in 2008, then Obamacare wouldn't have passed." Most people will admit that you can't prove statements like that, but it seems pretty clearly true that John McCain would not have signed the Affordable Care Act into law. But if statements have to correspond to reality to be true, then what part of reality does "If John McCain had won in 2008, then Obamacare wouldn't have passed" correspond to?

Just plain old reality, Lewis answered. To him, "If John McCain had won in 2008, then Obamacare wouldn't have passed" literally means that there are a bunch of real universes in which McCain won, and Obamacare was passed in none of them. The statement corresponds to real facts about possible worlds, so it can be true like any other statement is true.

In a paper with the punny title "Possible Girls," Sinhababu argued that modal realism has another benefit. It means that everybody has a romantic partner — whether or not they have one in the universe they live in.

Here's how it works. The number of possible universes is basically infinite. So there's almost certainly, in Sinhababu's view, a possible world in which a girl or guy is romantically devoted to someone who fits my description exactly, or who otherwise just is me. Suppose for the sake of argument that the feeling is mutual (it of course isn't; I happen to have a girlfriend who I love very much and who inhabits the same world I do). What we'd have then are two people who are interested and romantically devoted to each other. Usually we call that "dating."

It's non-traditional, of course, and communication between partners in different modal universes is difficult if not impossible; it makes Skype relationships look like a literal honeymoon. But plenty of people have non-traditional relationships these days. Neil, I think, makes a convincing case. So take heart, lonely hearts. Given some pretty strong metaphysical assumptions, you might have a partner!