 In Logical Foundations of Probability (1950) Carnap had discussed Bayes’ theorem and promised to expand the discussion in a second volume. Carnap’s interest in Bayesianism grew, but that second volume never materialized, quite possibly because rapid development of the field was still under way at the time of Carnap’s death. As his work proceeded Carnap tended to explain probabilities by reference to events and propositions rather than speak overtly about sentences. A similar change appears in the rest of Carnap’s work as well. It is not clear, however, whether this amounts to a major change of view or a change in what he sees as the most felicitous mode of expression. As the years progressed Carnap tended to see the remaining differences between himself and his subjectivist co-workers as chiefly differences in emphasis. In any case the subjectivist tradition is now dominant in philosophical discussions of probability (Zabell 2007, 293). Richard Jeffrey, whose own work arose out of logical empiricism, carried on that tradition for 35 years after Carnap’s death. Jeffrey himself made major contributions including a principle for updating ones beliefs when the evidence one learns is not certain. The world knows this principle as “Jeffrey conditionalization”; he called it simply “probability kinematics”.