Why Care About Anthropics?

It matters!

There is an argument for God that no one has successfully refuted that provides, if correct, absurdly strong evidence for the existence of God. Unlike every argument from the Thomists, the argument is relatively straightforward and relies on only one controversial premise, one held by many atheists! So far, the number of people who have written rebuttals is precisely one, and that rebuttal has involved rehashing generic arguments against God that can be demonstrably shown to not undermine the evidential significance of the argument one bit and objecting to the broad theory that the argument is based on while not understanding that they’re doing that, and then ignoring every argument for that theory, including some extremely conclusive demonstrations that the theory is right. Oh, and then trying to explain away the evidence by positing “stocking horse” theories which either have a prior of zero or predict the data with probability zero.

I’m not intending to criticize Truth Teller, who wrote that rebuttal. He’s quite a smart guy and his response was, in fact, many times more interesting and thoughtful than anything else that has been said in response. My point is that there have not been remotely convincing responses given to the argument, despite its quite overwhelming evidential force. To quote Amos Wollen’s parody of Peter Hitchens, “I’ve been universally ignored by everyone. I have not been listened to, even once—and I’m bored of it.”

Even the scores of sophisticated theists, people who usually think very carefully about these arguments, mostly say of the argument “hmm, that’s interesting,” and then ignore it. Theists who are quick to jump on the bandwagon when someone has a new argument from grounding or psychophysical harmony have ignored this argument, at most saying only “that’s interesting, might work,” with basically two exceptions: Amos and Apologetics Squared (first name Apologetics, last name Squared).

Why has this overwhelmingly powerful argument been essentially universally ignored, unlike other arguments—psychophysical harmony, for instance—that are similarly hard to understand? There is, of course, the fact that it wasn’t proposed by some hotshot philosopher like Dustin, but just undergraduate canine philosophy blogger Bentham’s Bulldog!

(Literally me).

But the other reason is that it has to do with the dreaded area of anthropics, reasoning about one’s existence. And people ignore anthropics because it’s confusing. As Aron Wall says, representing the consensus view about anthropics, “Pretty much all viewpoints lead to some horrendous paradoxes.” But do they? No, you only get horrendous paradoxes if you reject the self-indication assumption. That’s the theory that says that from your existence, you should think there are more people. Here’s a way to illustrate it, consider this case:

God’s extreme coin toss: You wake up alone in a white room. There’s a message written on the wall: “I, God, tossed a fair coin. If it came up heads, I created one person in a room like this. If it came up tails, I created a million people, also in rooms like this.” What should your credence be that the coin landed heads?

SIAers saw you should think tails is 1 million times likelier than heads. The reasoning is simple: if there are a million times as many people, then the odds you’d exist are a million times higher. So is Wall right that all theories get horrendous paradoxes? If you reject SIA, you get horrendous paradoxes including:

1. Either violating quite straightforward Bayesian updating AND the conservation of evidence or being able to predict you’ll get a royal flush in advance because if you don’t you’ll have a bunch of kids.

2. Thinking that the odds of you coming from a big family depends on whether other people who are not your parents have kids.

3. Thinking you can move boulders with your mind.

4. Saying that your anthropic reasoning depends greatly on whether other people are created and then die, or just not created.

5. Disagreeing in some egregious way with the presumptuous hatcher.

6. Positing bizarre and wholly unmotivated distinctions or denying that the fact that you exist gives you evidence that your parents didn’t use effective contraception.

The troubling results of SIA:

1. You should think the universe has a bunch of people because then it’s likelier to have you. In fact, you should think, for any two bunches of people it might have, it has the bigger one. This is supposedly a troubling presumptuousness, even though all theories of anthropics are presumptuous and this is basically just straightforward probabilistic reasoning!

2. Stuff gets weird with infinity, as it does in basically every area, including in anthropics, on every view.

I don’t know if philosophical theories get more lopsided than theories of anthropics. While it’s a tricky topic to think through, once you do, the best theory is quite clear, more so than in any other area of philosophy, or so I think. Implying crazy results just isn’t something that both theories do. If you think that this is a both-sides issue, something something white moderate, and you’re on the side of colonizers!!! It’s only one side that requires weird and paradoxical things over and over again, and the other that has only one slightly troubling result, which isn’t even that troubling and just seems like straightforward probabilistic reasoning.

Anthropics is worth caring about. It has very important implications for what ultimate reality looks like. It’s one of those areas of philosophy that rewards hard-work, where once you really think about it, it stops being a confusing mess and starts to actually make sense! It combines being tricky and fun with being genuinely figureoutable in a way not as true of, say, infinite ethics (if there is a solution to infinite ethics, it is known only by God and the angels and maybe Alexander Pruss).

Everyone says anthropics is tricky. But it’s only tricky when you have the wrong theory. Once you think about it correctly, it all starts to make sense. It rewards careful and clear thought and is mutually reinforcing: thinking through the inverse gambler’s fallacy charge helps you think through theories of anthropics more broadly, like SIA and SSA, and also through more specific puzzles like God’s coin-toss and doomsday.

There is, however, a danger of studying anthropics. If you think hard about it to the point where it makes sense, you will have to spend the next many decades of your life listening to people say completely crazy things about anthropics.