This is our monthly thread for collecting these little gems and pearls of wisdom, rationality-related quotes you've seen recently, or had stored in your quotesfile for ages, and which might be handy to link to in one of our discussions.
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I think I can explain both sides of this disagreement.
A Bayesian is someone who is, at some level of abstraction, keeping track of their entire hypothesis space. "Updating," for a Bayesian, means paying more attention to the part of yourself that predicted what you just saw happen. If a Bayesian says that they updated towards believing in God, they mean that they are paying more attention to the small part of themselves that already believed in God. "I assign a probability of 0 to God" means that no part of you believes in God, so there is no possibility of updating. You can't shift attention towards a part of yourself that isn't there.
Humans who say that they assign a probability of 0 to God, but who also claim that they could update, are not keeping track of the entire hypothesis space within their own brains. They are also using other brains to do that. There is no part of these humans that believes in God, but they would be able to copy this part from other humans if they ever needed to. These humans do not see themselves as trying to create a complete Bayesian within their own single brain; rather, they are trying to be part of a multiple-brain process that is doing something Bayesian. It does not matter as much to them which particular brains are paying attention to God.
I like your model, or something similar. The way I would do it, though, is to claim that my own decision-making is done by a committee of rational Bayesian minds - all resident within my head. Right now, the chairman of the committee assigns 0 to the probability that God exists. However, should we have a black swan event like a Rapture, then the chairman is helpless - he cannot update. No problem, though, because the other members of the committee were not so foolish as to become strong atheists. They will simply assassinate the now-useless former chairman of the Committee for Allowing Perplexed to Exhibit Rationality (CAPER) and replace him with a theist. The mind is under new management, but the body marches on.