Un grain de sable

This is a follow-up of the previous post . The debate on fine tuning and multiverses hinges on complex issues related to Bayesian reasoning. An influential argument from White in particular seems to show that we cannot infer the existence of the multiverse from our evidence of fine tuning. (White’s argument is apparently the main reason Philip Goff rejects the multiverse hypothesis, since most of his examples come from this particular paper.) The argument rests on the requirement of total evidence that White illustrates with this example:  Suppose I’m wondering why I feel sick today, and someone suggests that perhaps Adam got drunk last night. I object that I have no reason to believe this hypothesis since Adam’s drunkenness would not raise the probability of me feeling sick. But, the reply goes, it does raise the probability that someone in the room feels sick, and we know that this is true, since we know that you feel sick, so the fact that someone in the room feels sick is evid...

There has been a discussion on Twitter regarding the view, expressed by Philip Goff, that the multiverse hypothesis is not a good explanation for fine-tuning (or, as he would probably say, cannot be inferred from the fine-tuning of our universe). Short summary of Philip’s position The constants of our universe seem to be fine tuned for life, which would be miraculous. How can we explain this? An apparently good explanation is a multiverse hypothesis together with a selection effect. The idea is that there are many universes with different values for constants, so the fact that some of them are suitable for life is not miraculous, and of course, we happen to be in such a universe. According to Philip, an inference to this explanation is fallacious. It is an inverse gambler fallacy: seeing a double six when entering a casino, and inferring that there were many trials. The usual response is that it is not, because of a selection effect. If we are only allowed to enter the casino when ...