In this essay I want to look at some questions concerning the relation between morality and rationality in the recommendations they make about the best way to live our lives and achieve our good. Specifically, I want to examine ways in which the virtue of practical rationality (conceived in neo-Humean terms as the most authoritative practical excellence) and the various moral virtues might be thought to part company, giving an agent conflicting directives regarding how best to live her life. In conducting this enquiry, I shall at some crucial points be presupposing something of an Aristotelian perspective, but only in the most general way.

In what follows, I shall distinguish reason, the faculty or power, from rationality, the excellence or virtue (taken in the broadest sense) of that faculty. By practical reason I mean that part of reason that tells us what to do and how to live. By practical rationality (or, henceforth, rationality) I mean the excellence of that part of reason in virtue of which an agent is practically rational as opposed to irrational. By a neo-Humean conception of rationality I mean one that makes the goal of practical reason the maximal satisfaction of an agent's desires and preferences, suitably corrected for the effects of misinformation, wishful thinking, and the like. There are various versions of neo-Humean theory, and I shall not here be concerned with their specific differences.