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Comment by putzdown | Hacker News Reader

Every time I read about the Anthropic principle I get the feeling I'm missing something. Enthusiasts of the principle seem to be committing a fallacy; perhaps someone can explain why they're not, or why they are. I compare the principle to this. A group of friends get together and decide they'll roll a d20 to decide how to spend the evening. There are various options afoot, but they decide that only if they roll a 20 will they play board games that night. Lo and behold, they roll a 20 and spend the evening playing board games. Later someone says, "How lucky we are to be playing board games!" A skeptic says, "Whatever do you mean by 'lucky'?" Reply: "Well, there was a 1 in 20 chance, and we hit it! That's pretty lucky." The Anthropicist snorts and says, "Hardly! We're not lucky at all. There was a 100% chance. After all, we're playing them." Is that a good analogy? Or does it miss something crucial on one side of the argument or the other?

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Here's a better analogy. Joe has OCD. Every morning, he rolls a d100, and if it comes up 1, he hosts a board-game party that night.

On day XX/YY/ZZZZ, Joe hosts a board-game party and a bunch of people show up. During the course of the party, Joe reveals to everyone his d100 policy.

Tim asks him what his die-roll this morning was. Joe tells Tim that he rolled a 1. Tim exclaims "The only reason we're here is because you rolled a 1! How did this incredible piece of luck come to pass?"

Adam responds "There's nothing incredible about what happened. If Joe hadn't rolled a 1 today, we wouldn't be here. We would never have this discussion, or have it on some other day when he does roll a 1."

To extend this even further...

~This~ morning Joe rolled a dice, and it came up 1, so he hosted a board-game party.

During the party Joe hints that the die he rolls may be very large, but stops short of outright saying so.

Joe also refuses to say whether he rolls the die every morning, or if it was just this morning.

The interesting questions are:

How big is the die?

How often is it rolled?

Does Joe do anything at all if he rolls almost anything other than a 1, or does he just lie in bed?

If the very large die is only rolled once, and all non-1s are very boring, then it is remarkable that we're here.

"Does Joe do anything at all if he rolls almost anything other than a 1, or does he just lie in bed? If the very large die is only rolled once, and all non-1s are very boring, then it is remarkable that we're here."

That's a very interesting point you raised, and I was thinking about this as well. If the universe only "exists once", and life is very unlikely but it still came to be, then it does seem remarkable.

However, this is based on the presumption that life is non-boring, and all other potential universes devoid of life are boring. This seems like a very subjective presumption. Clearly we are biased towards thinking that our own existence, or the similar existence of "life" is special. But a skeptic would claim that from a purely scientific perspective, there's no reason to believe that a universe without life is any more boring than our universe.

Life aside, in a slightly different universe, it's unclear whether space or chemistry or atoms would even be possible: https://en.m.wikipedia.org/wiki/Fine-tuned_Universe

To quote neutral milk hotel, "how strange it is to be anything at all"

Well, but there is something fundamentally and essentially special about conscious minds. A universe that is complete unperceived is, first of all, harder to even imagine than it first appears and, second, would be neither boring nor interesting, since both of those words, and all other assessments, only have meaning within the context of conscious perception. So I would affirm the presumption that "life", in the sense of the existence of conscious minds, is non-boring and universes devoid of life are either boring, or inconceivable.

Spoken like a conscious mind

Ah, thanks. That's helpful. So would you say that the appeal of the Anthropic principle depends on the multiverse theory (or something similar): the idea that there are an infinite number—or a great many, anyway—of "die rolls", an infinite number of attempts?

Yes. Although you don't need an infinite number of universes. A very large number of years and a very large number of stars will do.

e.g Q: out of billions of stars what is the chance that this discussion takes place at a planet that can support intelligent life?

A: high

Yes, though there is an important difference between the multiverse approach and the multi-star/multi-year approach. When we imagine the state of affairs in which many universes are created with random parameters, we tend to give those many universes great variety, and we require each one of them (in our imaginations) to be "fruitful" at least in producing a universe. But it's not clear that the mere presence of lots of years (as many as you like) or stars (as many as you like) are fruitful in the same way. To put it back in terms of Joe the die roller, it's as if Joe wakes up most mornings and just lies in bed all day, not rolling the die. Occasionally—one day in a billion—he rolls the die, and it's a trillion-sided die, say. But I suppose the point is the same: the Anthropic principle says that however unlikely conscious minds are, if they do appear (at whatever odds), then... well I'm not sure where to go from there. Then these minds will ask questions about their existence? But that doesn't seem a very remarkable insight.

The anthropic principle goes the other way. It says that if the questions about existence are being asked, then we don't need further explanation of the lucky die roll.

I think the anthropic principle is a response to the claim that that is a remarkable insight.

I'm curious what relevance Joe's OCD has to the story?

A less silly line of reasoning is trying to explain why the constants in physics have the values they do which permit life as opposed to the bulk of values that don't. One explanation for this is all possible universes exist so naturally we find ourselves in one compatible with us which is a kind of anthropic reasoning. Other possible explanations being they result from something we don't understand, or that God did it.

yet another explanation is the constants are just natural, but we couldnt figure it out yet how and why they are natural.

I get a sense that the idea behind the anthropic principle is that the subjective experience is antecedent to objective reality, perhaps similar to solipsism or panpsychism.

More like the universe rolls a die, and if it comes up d20^1000, it creates a group of friends playing board games. There's no possible way for the friends to be unlucky, because in the unlucky case they simply don't exist.

In your case, in 19/20 possible worlds, there will be a group of disappointed friends not playing board games. It is reasonable to look for an explanation of why one finds oneself in the 1/20 case and not in the 19/20 case.

In the anthropic principle, in (N-1) cases there is nobody there to ask the question. Therefore, given that there is an entity capable of asking the question, there is no need to explain why that entity happens to find itself in a universe where question-asking entities are possible. Given that the friends exist at all, there is no need to explain why they are playing cards.

The anthropic principle doesn't answer the question of why there is a universe at all, how many universes there are, have been, or will be, or how many universes have contained intelligence. All it says is that we should not be surprised to find ourselves in a universe where intelligent life is possible, since it would be impossible for us to find ourselves anywhere else.

The point is, you can't come up with a grand theory of why you're playing board games, it was chance.

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