The green cab question was changed from the original in a way that (I think) changes the logic. http://heatherlench.com/wp-content/uploads/2008/07/bar-hillel.p

The green cab question was changed from the original in a way that (I think) changes the logic. http://heatherlench.com/wp-content/uploads/2008/07/bar-hillel.pdf http://heatherlench.com/wp-content/uploads/2008/07/bar-hille... In the original, witnesses are only 80% accurate reporting color. In this version it's altered so that it's simply asserted that 80% of cabs in the neighborhood of the accident are green. With that revision it seems to me that you would not update your priors but actually replace them. "The mix of cabs is 85/15. Oh wait, it's actually 20/80 the other way." Edit: Ah, never mind. The paper gives both versions, specifically because the in second version you are supposed to throw away the prior.