Besides defending quantum computing day and night, having drinks with Cosmic Variance‘s Sean Carroll, and being taken out to dinner at lots of restaurants with tablecloths, the other highlight of my job interview tour was meeting a friendly, interesting, articulate divinity student on the flight from San Francisco to Philadelphia, who tried to save my soul from damnation.

Here’s how it happened: the student (call him Kurt) was reading a Christian theological tract, while I, sitting next to him, was reading Russell on Religion. (This is true.) I sheepishly covered the spine of my book, trying to delay the inevitable conversation — but it finally happened, when Kurt asked me how I was liking ole’ Bert. I said I was liking him just fine, thank you very much.

Kurt then made some comment about the inadequacy of a materialistic worldview, and how, without God as the basis of morality, the whole planet would degenerate into what we saw at Virginia Tech. I replied that the prevention of suffering seemed like a pretty good basis for morality to me.

“Oh!” said Kurt. “So then suffering is bad. How do you know it’s bad?”

“How do you know it’s bad?”

“Because I believe the word of God.”

“So if God said that suffering was good, that would make it good?”

I can’t remember Kurt’s response, but I’m sure it was eloquent and well-practiced — nothing I said really tripped him up, nor did I expect it to. Wanting to change the subject, I asked him about his family, his studies, his job, what he’d been doing in the vipers’ den of San Francisco, etc. I told him a little about quantum computing and my job search. I mused that, different though we were, we both valued something in life more than money, and that alone probably set us apart from most people on the plane. Kurt said it was fitting that I’d gone to grad school at Berkeley. I replied that, as a mere Democrat, I was one of the most conservative people there.

Finally I blurted out the question I really wanted to ask. In his gentle, compassionate, way, Kurt made it clear to me that yes, I was going to roast in hell, and yes, I’d still roast in hell even if I returned to the religion of my ancestors (that, of course, being at best a beta version of the true religion). In response, I told Kurt that when I read Dante’s Inferno in freshman English, I decided that the place in the afterlife I really wanted to go was the topmost layer of hell: the place where Dante put the “righteous unbaptized” such as Euclid, Plato, and Aristotle. There, these pre-Christian luminaries could carry on an eternal intellectual conversation — cut off from God’s love to be sure, but also safe from the flames and pitchforks. How could angels and harps possibly compete with infinite tenure at Righteous Unbaptized University? If God wanted to lure me away from that, He’d probably have to throw in the Islamic martyr package.

San Francisco to Philadelphia is a five-hour flight, and the conversation ranged over everything you might expect: the age of the earth (Kurt was undecided but leaning toward 6,000 years), whether the universe needs a reason for its existence external to itself, etc. With every issue, I resolved not to use the strongest arguments at my disposal, since I was more interested in understanding my adversary’s reasoning process — and ideally, in getting him to notice inconsistencies within his own frame of reference. Alas, in that I was to be mostly disappointed.

Here’s an example. I got Kurt to admit that certain Bible passages — in particular, the ones about whipping your slaves — reflected a faulty, limited understanding of God’s will, and could only be understood in the historical context in which they were written. I then asked him how he knew that other passages — for example, the ones condemning homosexuality — didn’t also reflect a limited understanding of God’s will. He replied that, in the case of homosexuality, he didn’t need the Bible to tell him it was immoral: he knew it was immoral because it contradicted human beings’ biological nature, gay couples being unable to procreate. I then asked whether he thought that infertile straight couples should similarly be banned from getting married. Of course not, he replied, since marriage is about more than procreation — it’s also about love, bonding, and so on. I then pointed out that gay and lesbian couples also experience love and bonding. Kurt agreed that this was true, but then said the reason homosexuality was wrong went back to the Bible.

What fascinated me was that, with every single issue we discussed, we went around in a similar circle — and Kurt didn’t seem to see any problem with this, just so long as the number of 2SAT clauses that he had to resolve to get a contradiction was large enough.

In the study of rationality, there’s a well-known party game: the one where everyone throws a number from 0 to 100 into a hat, and that player wins whose number was closest to two-thirds of the average of everyone’s numbers. It’s easy to see that the only Nash equilibrium of this game — that is, the only possible outcome if everyone is rational, knows that everyone is rational, knows everyone knows everyone is rational, etc. — is for everyone to throw in 0. Why? For simplicity, consider the case of two people: one can show that I should throw in 1/2 of what I think your number will be, which is 1/2 of what you think my number will be, and so on ad infinitum until we reason ourselves down to 0.

On the other hand, how should you play if you actually want to win this game? The answer, apparently, is that you should throw in about 20. Most people, when faced with a long chain of logical inferences, will follow the chain for one or two steps and then stop. And, here as elsewhere in life, “being rational” is just a question of adjusting yourself to everyone else’s irrationalities. “Two-thirds of 50 is 33, and two-thirds of that is 22, and … OK, good enough for me!”

I’ve heard it said that the creationists are actually perfectly rational Bayesians; they just have prior probabilities that the scientifically-minded see as perverse. Inspired by conversations with Kurt and others, I hereby wish to propose a different theory of fundamentalist psychology. My theory is this: fundamentalists use a system of logical inference wherein you only have to apply the inference rules two or three times before you stop. (The exact number of inferences can vary, depending on how much you like the conclusion.) Furthermore, this system of “bounded inference” is actually the natural one from an evolutionary standpoint. It’s we — the scientists, mathematicians, and other nerdly folk — who insist on a bizzarre, unnatural system of inference, one where you have to keep turning the modus ponens crank whether you like where it’s taking you or not.

Kurt, who looked only slightly older than I am, is already married with two kids, and presumably more on the way. In strict Darwinian terms, he’s clearly been more successful than I’ve been. Are those of us who can live with A→B or B→C or C→not(A) but not all of them at once simply evolutionary oddities, like people who have twelve fingers or can’t stand sunlight?