The concept of welfare plays a central role in the theory of prudence. It is an
analytic truth that we are prudentially obligated to maximize our own welfare.
Substance is added to this shell of a theory of prudence when a theory of welfare is
supplied. Many theories of rationality also require a theory of welfare for
completeness. One conception of rationality, for instance, says that an action is rational
if and only if it maximizes expected welfare.