Several global justice theorists, in responding to Kantian concerns about the coherence of human rights talk, have defended something like the following: duties to improve the welfare of others may look imperfect, but this is no barrier to seeing those duties as correlative to welfare rights, because imperfect duties can be converted into perfect duties. I show that this line of argument depends on conflating the Kantian understanding of imperfect duty with a more recent liberal understanding. Once we disentangle the two understandings, it can be seen that conversion is impossible on the Kantian understanding. I argue that, whatever we want to call it, the Kantian distinction captures something deeply important to practical philosophy, and we should accept that Kantian imperfect duties cannot be converted into (either liberal or Kantian) perfect duties - and so cannot correlate to rights.
