ABSTRACT
An autonomy thesis maintains that facts or propositions in some domain are isolated in some respect from those in some other domain, or perhaps all other domains. This chapter explores the general question of the autonomy of the ethical domain from the non-ethical domain. It discusses three types of ethical autonomy thesis, distinguished by the types of relation maintained not to obtain between the antecedents and consequents in arguments such as these: logical relations, metaphysical relations, and epistemic relations. The chapter suggests that the real motivation for metaphysical and logical autonomy arises from the importance of an epistemological thesis, namely the thesis that non-ethical propositions are irrelevant to the justification of non-derivative ethical propositions. Versions of non-identity restricted to value or morality are inconsistent with familiar brands of ethical naturalism: straightforward reductive realism, analytical naturalism and synthetic naturalism. One can use metaphysical autonomy as a fulcrum to argue that many enthymematic premises are ethical principles.
