Traditional arguments for moral error theory are based on identifying a problem with the metaphysics of moral properties. I provide a new argument that is based on the inconsistency of first‐order moral judgments. I illustrate this using impossibility results in population axiology.

An indeterminate version of Henry Sidgwick’s “Dualism of Practical Reason” may offer a solution to Derek Parfit’s “Repugnant Conclusion”. Here we will outline the problem of Sidgwick’s Dualism and how to resolve it within the framework of practical reason and the problem of Parfit’s Repugnance and why it is irresoluble within the framework of pure utilitarianism. Then we will argue how Sidgwick’s Dualism, under certain formulations of indeterminacy, specifically under those Indeterminacy Views advanced by David Phillips (and others), implies a (...) resolution to the Repugnant Conclusion that is both intuitive and simple, resolving Sidgwick’s Dualism and Parfit’s Repugnance in one conceptual move. (shrink)