Christine Korsgaard’s argument for the claim that one should not only value one’s own humanity but also the humanity of all other persons, ‘the publicity of reasons argument’, has been heavily criticized and I believe rightly so. However, both in an early paper and in her most recent work, Korsgaard does not rely on controversial, Wittgensteinian ideas regarding the publicity of reasons, but instead she uses a different argument to justify interpersonal morality, which I will refer to as ‘the argument (...) from the sufficiency of agency’. The goal of this paper is to evaluate whether the argument from the sufficiency of agency can succeed where the publicity of reasons argument fails. I will argue that although the argument from the sufficiency of agency is potentially more promising, it fails to justify a categorical and universal principle of interpersonal morality. I argue, however, that this failure has less to do with the argument from the sufficiency of agency itself and more with Korsgaard’s specific version of it. This leaves open the possibility that other Kantian constructivist arguments from the sufficiency of agency might be more successful. (shrink)