 Some critics argue that Korsgaard’s argument rests on realist premises, and thus it is not a complete alternative to moral realism (Watkins &amp; Fitzpatrick 2002; Fitzpatrick 2005; Ridge 2005; Stieb 2006; Kain 2006a,b; Papish 2011; O’Shea 2015; Schafer 2015a. To this extent, her defense of Kantian constructivism does not offer a distinctive reply to skeptical challenges to ethical objectivity. According to others, Korsgaard’s argument is vulnerable to the objection of ‘regress on conditions’, which says that it is not logically necessary that the condition of a thing’s value be valuable itself (Rabinowicz &amp; Rønnow-Rasmussen 2000; Kerstein 2001; Ridge 2005; Coleman 2006). That is to say that humanity may be the condition of the possibility of value and yet lack value itself.