This project aimed to apply the powerful tools of decision theory to provide novel arguments for the epistemic norms that we take to govern what it is rational to believe; and to discover new epistemic norms. We treat the possible epistemic states of an agent as if they were epistemic actions between which that agent must choose. And we consider how we should measure the purely epistemic utility of being in such a state. We then apply the general apparatus of decision theory to determine which epistemic states are rational in a given situation from a purely epistemic point of view; and how our epistemic states should evolve over time. This allows us, often for the first time, to give formal justifications of epistemic norms without appealing to pragmatic considerations that seem intuitively irrelevant to the norms in question. These formal arguments have the great advantage that their assumptions are made mathematically precise and their conclusions are deduced from their assumptions by means of a mathematical theorem. We call their study epistemic utility theory.