 A variety of non-consequentialist arguments are offered as well. Kirp, Yudof, and Franks, for example, refer to Kant’s categorical imperative and claim that treating individuals as self-owners is what is meant by treating individuals as ends in themselves ((Kirp, et al. 1986: 13–14). Wendy McElroy grounds her thought in the natural law tradition (McElroy 1998b). Some imply a perfectionist justification according to which the perfection of the human being requires being treated as a self-owner (Presley 2001).