On the Alleged Impossibility of Bayesian Coherentism

The success of Bovens and Hartmann’s recent "impossibility result" against Bayesian Coherentism relies upon the adoption of a specific set of ceteris paribus conditions. In this paper, I argue that these conditions are not clearly appropriate; certain proposed coherence measures motivate different such conditions and also call for the rejection of at least one of Bovens and Hartmann's conditions. I show that there exist sets of intuitively plausible ceteris paribus conditions that allow one to sidestep the impossibility result. This shifts the debate from the merits of the impossibility result itself to the underlying choice of ceteris paribus conditions. B&H on Bayesian Coherentism In several recent publications [(2003), (2005), (2006)], Luc Bovens and Stephan Hartmann (hereon, “B&H”) present their "impossibility result" for Bayesian Coherentism. They understand Bayesian Coherentism essentially to be the conjunction of the following three fundamental tenets [(2006, pp. 78-9), (2003, pp. 11-12, 25)]: • Separability (BC1): For all information sets S, S' S, if S is no less coherent than S', then our degree of confidence that the content of S is true is no less than our degree of confidence that the content of S' is true, ceteris paribus. • Probabilism (BC2[i]): The binary relation of "...being no less coherent than..." over S is fully determined by the probabilistic features of the information sets contained in S. • Ordering (BC2[ii]): The binary relation of "...being no less coherent than..." is an ordering; i.e., the relation is transitive and complete. i