Because
This chapter responds to J. L. Mackie’s challenge to show just what there is in reality that supports claims about what is valuable and obligatory. It seeks to explain the relationship between a moral fact and a non-moral one and to consider the charge that perfectionism of any form commits the so-called naturalistic fallacy. In so doing, five ways of understanding the supposed gap between what is and what is valuable—that is, the ontological, logical, semantic, epistemological, and motivational gaps—are considered (along with some of the views of David Hume, G. E. Moore, Simon Blackburn, and Stephen Darwall). It is argued that individualistic perfectionism, which is grounded in a life-based, non-reductionist naturalistic account of teleology (which is in certain ways like that of Philippa Foot’s), does not commit any fallacy and that it can meet Mackie’s challenge.