The social diffusion of warrant and rationality

Many people agree that a proper epistemological treatment of testimonial knowledge will regard testimonial warrant - the total truth-conducive support enjoyed by a belief grounded on a piece of testimony - as socially diffuse, in the sense that it is not something that supervenes on the proper functionality of the hearer's cognitive resources together with the reasons she has for accepting the testimony. After arguing for such a view, I go on to identify a challenge many people think flows from an acknowledgment of the social diffusion of warrant. In particular, such an acknowledgment appears to preclude a happy account of the rationality of testimony-based belief. After identifying the nature of this challenge and the various positions that one can take on it, I develop a response according to which rationality itself (like warrant) is socially diffuse.