Full Idea
Jeffrey produced a version of Bayesianism that made no direct use of gambling (as Ramsey had), but treats the objects of preference ...as propositions.
Gist of Idea
Instead of gambling, Jeffrey made the objects of Bayesian preference to be propositions
Source
report of Richard Jeffrey (The Logic of Decision [1965]) by Donald Davidson - Truth and Predication 3
Book Reference
Davidson,Donald: 'Truth and Predication' [Belknap Harvard 2005], p.67
A Reaction
I'm guessing that Jeffreys launched modern Bayesian theory with this idea. It suggest that one can consider degrees of truth, rather than mere winning or losing.