Anthropic selection is not magic. More precisely, it is the least amount of magic necessary to ensure our existence.
If a miracle is necessary for you to survive, but either a smaller miracle or a (much) greater miracle can do the job, then if you survive, you should expect that it was because of the smaller miracle.
Multiple independent improbabilities are multiplied, so similarly if you can be saved by either one miracle alone or ten independent miracles of comparable size, then if you survive, you should expect to be saved by the one miracle.
(It all adds up to the nearest possible approximation of normality.)
So my guess is that the argument implicitly made by Julia and/or Toby (I haven’t read the book nor listened to the episode) could be that although it is technically possible that we have avoided nuclear extinction because of a sequence of lucky outcomes, when you multiply the probabilities, the result is so small that there is probably something else (perhaps also some kind of luck, but smaller in magnitude than this entire sequence combined) responsible for the outcome.
In other words, you should not accept the answer “you were saved by a miracle of a probability P” before you have sufficiently explored possible miracles with probabilities greater than P. (Even if you believe that you were saved by anthropic magic.)
When I try to think anthropically about nuclear extinction specifically, it seems to me that there are also possible outcomes other than “no nuclear war” and “humanity extinct”. Like situations where (most of) USA and USSR (and a few other countries) were nuked, but many places were not nuked, people survived there, and even the nuclear winter or whatever didn’t literally kill all humans. If there were many nuclear “near misses”, then there should be also many alternative histories like these. After enough such branches, even with anthropic reasoning, the probability of finding ourselves as survivors in a post-apocalyptic world is greater that the probability of finding ourselves in a world without a nuclear war. Not sure about exact numbers, though. The opposing argument is that the world without a nuclear war contains much more humans than any individual post-apocalyptic world.
Thanks. By “smaller miracle,” are you referring to the case that Julia’s estimates are wrong? Or something else?
Agreed that expecting a high fraction of observers to survive a nuclear war makes anthropic selection a less-appealing explanation. Would be interesting to see the numbers.
I interpret Julia’s “I would have put a probability of maybe 25% on a lot of those. But it starts to add up. [...] which kind of throws into question my ability to assign good probabilities to all of these near misses.” to mean that the 25% estimates are either wrong or not independent, because there were too many such events, and the multiplied probabilities of being lucky at all of them is just too small.
So there is probably some other explanation… but Julia in the quoted text does not propose a specific alternative. She just says that if there was only one such event in history, then explanation “25% extinction, 75% we got lucky” would be a good explanation of our current state; but now that she knows there were actually many such events, it does not seem like a good explanation anymore.
Anthropic selection is not magic. More precisely, it is the least amount of magic necessary to ensure our existence.
If a miracle is necessary for you to survive, but either a smaller miracle or a (much) greater miracle can do the job, then if you survive, you should expect that it was because of the smaller miracle.
Multiple independent improbabilities are multiplied, so similarly if you can be saved by either one miracle alone or ten independent miracles of comparable size, then if you survive, you should expect to be saved by the one miracle.
(It all adds up to the nearest possible approximation of normality.)
So my guess is that the argument implicitly made by Julia and/or Toby (I haven’t read the book nor listened to the episode) could be that although it is technically possible that we have avoided nuclear extinction because of a sequence of lucky outcomes, when you multiply the probabilities, the result is so small that there is probably something else (perhaps also some kind of luck, but smaller in magnitude than this entire sequence combined) responsible for the outcome.
In other words, you should not accept the answer “you were saved by a miracle of a probability P” before you have sufficiently explored possible miracles with probabilities greater than P. (Even if you believe that you were saved by anthropic magic.)
When I try to think anthropically about nuclear extinction specifically, it seems to me that there are also possible outcomes other than “no nuclear war” and “humanity extinct”. Like situations where (most of) USA and USSR (and a few other countries) were nuked, but many places were not nuked, people survived there, and even the nuclear winter or whatever didn’t literally kill all humans. If there were many nuclear “near misses”, then there should be also many alternative histories like these. After enough such branches, even with anthropic reasoning, the probability of finding ourselves as survivors in a post-apocalyptic world is greater that the probability of finding ourselves in a world without a nuclear war. Not sure about exact numbers, though. The opposing argument is that the world without a nuclear war contains much more humans than any individual post-apocalyptic world.
Thanks. By “smaller miracle,” are you referring to the case that Julia’s estimates are wrong? Or something else?
Agreed that expecting a high fraction of observers to survive a nuclear war makes anthropic selection a less-appealing explanation. Would be interesting to see the numbers.
I interpret Julia’s “I would have put a probability of maybe 25% on a lot of those. But it starts to add up. [...] which kind of throws into question my ability to assign good probabilities to all of these near misses.” to mean that the 25% estimates are either wrong or not independent, because there were too many such events, and the multiplied probabilities of being lucky at all of them is just too small.
So there is probably some other explanation… but Julia in the quoted text does not propose a specific alternative. She just says that if there was only one such event in history, then explanation “25% extinction, 75% we got lucky” would be a good explanation of our current state; but now that she knows there were actually many such events, it does not seem like a good explanation anymore.