Mozart's great opera, Don Giovanni, poses a number of significant philosophical and aesthetic challenges, and yet it remains, for the most part, little discussed by contemporary philosophers. A notable exception to this is Bernard Williams's important paper, ‘Don Juan as an Idea’, which contains an illuminating discussion of Kierkegaard's ground-breaking interpretation of the opera, ‘The Immediate Erotic Stages or the Musical-Erotic’, in Either/Or. Kierkegaard's pseudonymous author's (A) approach here is, in some respects, reminiscent of a currently rather fashionable narrative-inspired moral philosophy, of which Williams himself is perhaps the most impressive recent exponent. In the light of this apparent methodological confluence, Williams's disagreement with A about the meaning of Don Giovanni's final two scenes seems particularly significant. By offering an interpretation of Don Giovanni that both retains A's fundamental ideas and manages to get round the problems in Williams's account, I will show that the greatness of Mozart's opera is largely a function of the challenge it presents to the ‘morality system’.