 Why construct formal representations of belief? To a large extent, the rigours and rewards of formalism in epistemology are the same as they are in any other discipline. It requires that we state basic principles precisely, and in return it permits us to demonstrate, whether by deductive proof or  computer simulation,  their logical consequences and connections. Often, these consequences and connections are unexpected—sometimes so unexpected that it is hard to imagine how they could have been discovered without the aid of the formalism. If an attractive-looking principle has an unattractive consequence, it is easy to imagine how one might have been tempted to evade or ignore it, had it not been so clearly demonstrated. Perhaps the most common tragedy is to find that several attractive principles are mutually inconsistent and that some unpleasant sacrifice must therefore be made. After a few such experiences, the epistemologist comes to feel that formal representations forestall equivocation and self-deception and promote progress and understanding. 