 Ramsey (1926) avoids the first difficulty by pricing bets in utility instead of money. He avoids the second difficulty by presupposing the existence of at least one “ethically neutral” proposition (a proposition whose truth or falsity is a matter of indifference) which the agent takes to be just as likely to be true as she takes it to be false. See Section 3.5 of the entry on  interpretations of probability.  Nevertheless, the bearing of the preceding examples is that fair betting ratios and subjective probabilities can easily come apart. Subjective probabilities are measured by, but not identical to, (fair) betting ratios. The latter are operationally defined and observable. The former are unobservable, theoretical entities that, following Eriksson &amp; Hájek (2007), we take as primitive.