 While both steps of the argument are controversial, the second stage has come in for especially heavy fire. (For a careful discussion of the dialectic, see Suikkanen 2010; for an ingenious argument against Jackson that identity with descriptive properties is compatible with ethical non-naturalism, see Dunaway 2017). One important general basis for doubt is that many contemporary philosophers question whether modality constitutes the fundamental explanatory currency of metaphysics, as Jackson and Brown seem to presuppose (for an especially influential challenge see Fine 1994, for an especially radical challenge, see Sider 2011, Ch. 12).