In this paper, I distinguish between two error theories of morality: one couched in terms of truth ; the other in terms of justification. I then present two arguments: the Poisoned Presupposition Argument for ET1; and the Evolutionary Debunking Argument for ET2. I go on to show how assessing these arguments requires paying attention to empirical moral psychology, in particular, work on folk metaethics. After criticizing extant work, I suggest avenues for future research.