This chapter distinguishes six different kinds of rationality which a belief may possess. It may be rational in being probable, given the believer's evidence and his or her inductive criteria; or probable, given the believer's evidence and correct inductive criteria. Or it may be rational in being the result of what the believer regards as adequate investigation, or the result of adequate investigation by the believer's own criteria, or the result of adequate investigation by correct criteria. Or it may be rational in being brought about by some process satisfying some externalist (e.g., reliabilist) criterion. Correct criteria require a subject to investigate the truth of a proposition in so far as its initial probability is not very close to l or 0, there is an initial probability that investigation will change the probability, and having a true belief on the issue is important relative to other demands on the subject's time.
Keywords: belief, investigation, evidence, probability