Acting on Belief Functions
--------------------------

The degrees of belief of rational agents should be guided by
the evidence available to them.  This paper takes as a
starting point the view -- argued elsewhere -- that the
formal model best able to capture this idea is one that
represents degrees of belief using Dempster-Shafer belief
functions.  However degrees of belief should not only
respect evidence: they also guide decision and action.
Whatever formal model of degrees of belief we adopt, we need
a decision theory that works with it: that takes as input
degrees of belief so represented.  The task of this paper is
to develop such a decision theory for the belief function
model of degrees of belief.  This is not the first paper to
attempt that task, but compared to the existing literature
it takes a more abstract route to its destination, via a
consideration of the very idea of rational decision making
in light of one's beliefs and desires.  After presenting the
new decision theory and comparing it to existing views, the
paper goes on to consider diachronic decision situations.