Say that an agent is epistemically humble if she is less than fully confident that her opinions will converge to the truth, given appropriate evidence. Is such humility rationally permissible? According to Gordon Belot’s orgulity argument: the answer is yes, but long-run convergence-to-the-truth theorems force Bayesians to answer no. That argument has no force against Bayesians who reject countable additivity as a requirement of rationality. Such Bayesians are free to count even extreme humility as rationally permissible. Furthermore, dropping countable additivity does not render Bayesianism more vulnerable to the charge that it is excessively subjective.
For helpful comments and discussion, thanks to Andrew Bacon, Gordon Belot, Cian Dorr, Kenny Easwaran, Kevin Kelly, Bas van Fraassen, Jim Hawthorne, Teddy Seidenfeld, Brian Weatherson, Jonathan Wright, and anonymous reviewers. I thank John Burgess for introducing me to the dualities between measure and category when he was my junior paper advisor in spring 1995. For financial support I am grateful to the David A. Gardner ’69 Magic project (through Princeton University’s Humanities council), the PIIRs Research Community on Systemic Risk, and a 2014–15 Deutshe Bank Membership at the Princeton Institute for Advanced Study. For an extremely congenial work environment in July 2014, thanks to Mindy and Gene Stein.