Troubles on moral twin earth

moral queerness revived

Terence Horgan

Mark Timmons

pp. 221-260

in: Synthese 92 (2), 1992.

Abstract

J. L. Mackie argued that if there were objective moral properties or facts, then the supervenience relation linking the nonmoral to the moral would be metaphysically queer. Moral realists reply that objective supervenience relations are ubiquitous according to contemporary versions of metaphysical naturalism and, hence, that there is nothing especially queer about moral supervenience. In this paper we revive Mackie's challenge to moral realism. We argue: (i) that objective supervenience relations of any kind, moral or otherwise, should be explainable rather than sui generis; (ii) that this explanatory burden can be successfully met vis-à-vis the supervenience of the mental upon the physical, and in other related cases; and (iii) that the burden cannot be met for (putative) objective moral supervenience relations.