Stanley Cavell presents Moral Perfectionism as a set of methods of self-knowledge, aiming at the clarification of one’s understanding of oneself. Cavell also claims that Moral Perfectionism is a form or a dimension of moral reasoning. One might wonder, in this perspective, what relation can be drawn between perfectionist methods of self-knowledge and the practice of providing moral reasons for a certain action. In this paper, I propose to understand this connection on the background of Cavell’s account of moral reasoning in Part 3 of The Claim of Reason. Cavell here contrasts the rationality of moral discourse with arguments that recur in epistemological and scientific contexts. While in these latter areas of investigation, the activity of giving and asking for reasons serves to establish one’s position (i.e. one’s authority to enter a given claim), in morality the aim is rather one of making one’s position (that is, one’s cares and commitments) intelligible, both to others and to oneself. I argue that this account may enable us to clarify to sense in which, in Cavell’s perspective, perfectionism is both pertinent and vital for moral reasoning: since a dedication to self-knowledge is constitutive of moral discourse, the avoidance of such a dimension may impoverish and distort our conception of moral rationality.