I’m Screwtape, also known as Skyler. I’m an aspiring rationalist originally introduced to the community through HPMoR, and I stayed around because the writers here kept improving how I thought. I’m fond of the Rationality As A Martial Art metaphor, new mental tools to make my life better, and meeting people who are strange in ways I find familiar and comfortable. If you’re ever in the Boston area, feel free to say hi.
Starting early in 2023, I’m the ACX Meetups Czar. You might also know me from the New York City Rationalist Megameetup, editing the Animorphs: The Reckoning podfic, or being that guy at meetups with a bright bandanna who gets really excited when people bring up indie tabletop roleplaying games.
I recognize that last description might fit more than one person.
I’m not sure I’m following your actual objection. Is your point that this algorithm is wrong and won’t update towards the right probabilities even if you keep feeding it new pieces of evidence, that the explanations and numbers for these pieces of evidence don’t make sense for the implied story, that you shouldn’t try to do explicit probability calculations this way, or some fourth thing?
If this algorithm isn’t actually equivalent to Bayes in some way, that would be really useful for someone to point out. At first glance it seems like a simpler (to me anyway) way to express how making updates works, not just on an intuitive “I guess the numbers move that direction?” way but in a way that might not get fooled by e.g. the mammogram example.
If these explanations and numbers don’t make exact sense for the implied story, that seems fine? “A train is moving from east to west at a uniform speed of 12 m/s, ten kilometers west a second train is moving west to east at a uniform speed of 15 m/s, how far will the first train have traveled when they meet?” is a fine word problem even if that’s oversimplified for how trains work.
If you don’t think it’s worth doing explicit probability calculations this way, even to practice and try and get better or as a way to train the habit of how the numbers should move, that seems like a different objection and one you would have with any guide to Bayes. That’s not to say you shouldn’t raise the objection, but that doesn’t seem like an objection that someone did the math wrong!
And of course maybe I’m completely missing your point.