In a brief section of The Theory of Moral Sentiments that has often been overlooked, we find a fascinating discussion of the phenomenon of moral luck. This article argues that Adam Smith's discussion is important for two reasons: first, for what it tells us about the role our psychology, including some of its more 'irregular' features, plays in allowing us to reap the benefits of social cooperation and, second, for the novel solution it suggests to the problem of moral luck.