Richard Carl Jeffrey (August 5, 1926 – November 9, 2002) was an American philosopher, logician, and probability theorist.
He is best known for developing and championing the philosophy of radical probabilism and the associated heuristic of probability kinematics, also known as Jeffrey conditioning.
[3] Jeffrey, who died of lung cancer at the age of 76, was known for his sense of humor, which often came through in his breezy writing style.
In the preface of his posthumously published Subjective Probability, he refers to himself as "a fond foolish old fart dying of a surfeit of Pall Malls".
In Bayesian statistics, Bayes' theorem provides a useful rule for updating a probability when new frequency data becomes available.
If the learner subsequently learns that B is true, nothing in the axioms of probability or the results derived therefrom tells him how to behave.
In this case Bayes' rule isn't able to capture a mere subjective change in the probability of some critical fact.
It seems reasonable, as a starting position, to adopt the law of total probability and extend it to updating in much the same way as was Bayes' theorem.