Published online by Cambridge University Press: 01 January 2022
Probability theory is important not least because of its relevance for decision making, which also means: its relevance for the single case. The frequency theory of probability on its own is irrelevant in the single case. However, Howson and Urbach argue that Bayesianism can solve the frequentist's problem: frequentist-probability information is relevant to Bayesians (although to nobody else). The present paper shows that Howson and Urbach's solution cannot work, and indeed that no Bayesian solution can work. There is no way to make frequentist probability relevant.
I am very grateful to Donald Gillies, Colin Howson, and Alan Musgrave for preliminary discussions; to Paul Humphreys and Stefanie Mehret for comments on a first version; to Volker Gadenne; and to three anonymous referees. To one of the referees, I am especially indebted for many helpful suggestions.