 A fourth reply would be to shrug off the alleged explanatory challenge. However allegedly puzzling the combination of the features described by (1) and (2) are, they are consistent features of a concept. This means that we could choose to introduce a concept that exemplified those features. It might thus be suggested that Blackburn’s argument shows only that we have chosen to do so with our ethical concepts (compare Olson 2014, 89–90). One might reply to this last point that it is precisely this choice that needs to be explained. Blackburn argues that the non-cognitivist has a smooth functionalist explanation for why our ethical thought and talk includes the ban on mixed worlds (see  Section 3.3  below for discussion), while for the realist, this might just be an unexplained peculiarity of our choice of concepts.