Closure and Rational Belief

What kinds of principles belong in a theory of rational
belief? One contention of this paper is that it is impossible
to reach informed conclusions about the answer to this
question without a clear sense of what such a theory is
intended to do. It may be rejoined that such a theory is
always, at least, intended to cash out, in perspicuous
terms, the notion of rationality, and hence no further
context is needed to try and decide what principles belong
in the theory. This will not do: use of the term "rationality" is
so multi-faceted that it is doubtful whether there is a single
concept that it picks out. In fact, specifying what a theory of
rationality is intended to do may go hand in hand with
providing a characterization of one notion (out of many) of
rationality. This will prove to be the case in the following.