My wife is a political scientist who teaches, among other things, a quantitative methods course. You know what that means…statistics. But I’m a recovering sociologist, so I don’t mind. This morning she was feeling sick, so she decided to stay in bed and cancel her classes (this is very unusual). So I told her she should just watch some movies on her computer and she said “Yes–grab the statistics one down in the dining room for me!” Figures. Well, it was a stats class on DVD called something like What are the Chances? and it got me thinking that what this world needs is a rom-com based on probability.
There would be a counter below the main action that showed the odds of the two protagonists ever getting together, and little displays all over showing the odds of something happening (probability of coffee cup spilling: 1 in 50). Of course, in the end, a rapid series of events would lead the main counter to spin up to 1.0! and there would be a kiss, that sort of thing.
This got me thinking…since my spouse and I met in graduate school, I asked her what the odds were of her attending that grad school. She said she applied to 2, and go into 1 (her “safety school” didn’t accept her!) so the odds were pretty much 1.0 that she’d end up at Chicago. For me, I applied to 9 schools and got into 8, so that cut the odds of my going to Chicago to .125.
1 x .125 = .125 (the initial probability, given that both of us left our home towns for graduate school, that we’d both end up at the University of Chicago). Then you have to throw in the odds that we’d be there at the same time, and that the class would be cross-listed including both political science and sociology, that we’d each register for it, and that we’d actually even talk during the class. And then, that we’d like each other enough to keep talking, etc., etc., etc. Let’s assume that only those things matter (there are of course many more) and that the odds were 50/50 for each of those events (which substantially overstates the probability in every case). That means we have:
.125 x .5 x .5 x 5 x .5 = .008 (rounding up)
So, 8 chances in 1,000 right there. The odds that the relationship would survive to marriage and four children are of course even smaller. And also of course, this is all hoo-hah, since many of the events weren’t independent, etc., etc. But. This is the sort of thing that leads many couples to conclude that they were “meant for each other,” because the odds of their coming together were so vanishingly small.
This is also the sort of reasoning that creationists like to use to prove the existence of god. What are the odds that human beings would evolve? That just the right amino acids would form and combine, and that the Earth would be just the right distance from the Sun so that water would be available in liquid form, and so forth? How, under such conditions, could something as complicated as an Eye appear? The probability of each event, as they point out, is vanishingly small, and, as they also correctly point out, in the world of probability,
small x small = smaller
as I have already shown above. Ceteris paribus, the joint probability of two events is the product of their probabilities. The thing that the creationists leave out is the ceteris paribus, which means “all else being equal.” Thing is, it’s not. Had the Earth been much closer to or much farther away from the Sun, those amino acids might not have linked up at all, or they might have linked in different ways. The outcome would have been different. But the point is that amino acid formation and liquid water were both influenced by something else: our distance from the Sun. So were many other things that, collectively, favored the appearance and evolution of life. And once you have life, life that is better able to survive (starting with a basic sensitivity to light that enables predators to find you and you to avoid predators) tends to out-compete life isn’t. It’s not merely probability, and not everything is even nearly equal.
And there’s more. If we reason backward (as creationists are wont to do), then the probability of the world around us (and, more importantly, us) working out as it and we did is so vanishingly small as to stagger the imagination. But if we allow differences–I could’ve been left-handed, non-diabetic, far-sighted, shorter, taller–we start to see that things didn’t have to be this way. We might’ve turned out to be green, with a hive-mind. Any one of those myriad probabilities could have turned out differently, and the result would not be “us” as we are, but it would have been something. Or not. So the next time somebody tells you that god has pale skin and red hair and wears a white robe (because we are, after all, created in his image) remind them that such a view of probability dictates that god could as well look like, say, a flying spaghetti monster. Or like nothing at all. That we turned out the way we did proves nothing. I happen to like it, but it didn’t have to be this way.
I also happen to like my spouse. A lot. I’ve been in love with her for more than 28 years, come April. But it didn’t have to be that way. Had I never left Minnesota, I might never have married, or I might have met someone else I loved, or… It wasn’t written in stone. It wasn’t dictated by probability.
Now some might say that takes away the magic. “You’re arguing” (they would say) “that any number of other relationships might have worked out and been completely satisfying for you!” And they’re right. That’s exactly what I’m saying. But ceteris is not paribus. This was one of a number of relationships that probability threw my way, and her way, and it’s the one we mutually seized upon and worked at. We forged it. We built this marriage on rock and roll (or at least on folk music and pop). One night as we walked through a parking lot strewn with Autumn leaves, I realized that I couldn’t live without her.
Life is very much what you make of it, ceteris paribus. And since you have no choice about the ceteris, you might as well start making. So that’s my (late) Valentine’s Day post.
Make of it what you will.