All language is rule-governed, and the language of epistemology is no exception. The advent of the tools of modern symbolic logic has made it increasingly possible to investigate various uses of language by formalizing the language, i.e. enshrining the rules in a formal logic. Thus we have seen in the last century the development of modal logic (the logic of necessity and possibility), deontic logic (the logic of obligation and permission), temporal logic (the logic of time), and epistemic logic (the logic of knowledge and belief). The first attempt to formalize the language of epistemology seems to have been made by Georg von Wright (1951). Unfortunately, this was not a particularly penetrating analysis, being really tangential to von Wright's main purpose, which was an investigation into the logic of the alethic modalities. The first thoroughgoing epistemic logic was constructed by Hintikka (1962). (I shall label this system "KB' for ease of reference since, to the best of my knowledge, it has no other label, and its basic formulation is in Hintikka (1962).)