As a motive, self-interest is constituted by a certain kind of concern for oneself; but we also use the term “self-interest” to refer to the object of such a motive, to the well-being or good life sought by a self-interested agent. In this essay, I want to concentrate on self-interest in the latter sense and say something about how self-interest or well-being relates to virtue. One reason to be interested in this relationship stems from our concern to know whether virtue pays, i.e., is in the moral agent's self-interest, a question which Plato notably asks in the Republic and which has been of concern to moral philosophers ever since. But the importance for ethics of notions like virtue and self-interest is hardly exhausted by their role in the debate over whether virtue pays; indeed, any large-scale ethical theory will presumably have something to say about how these major notions relate, so we have reason to want to understand this relationship independent of the particular desire to show that morality or virtue is in the self-interest of the (virtuous) agent.
It will be a background assumption of this essay that some ways of connecting virtue and well-being/self-interest redound to the advantage of the larger theories that incorporate them. If, in particular, we believe in the bona fides of ethical theory, then unifying power is a desideratum in ethics and it stands in favor of utilitarianism (and Epicureanism) that it offers us a way of unifying our understanding of virtue and well-being. To be sure, that advantage may to some extent or ultimately be undercut if unification leads to counterintuitive ethical consequences.