Sympathy for the Error Theorist: Parfit and Mackie

Derek Parfit claims that “Williams and Mackie…do not use the normative concepts that I and other Non-Naturalists use.” Whatever we think of Parfit’s interpretation of Williams, his interpretation of Mackie should be rejected. For understandable historical reasons, Mackie’s texts are ambiguous. But if we apply to the interpretation of Mackie the same principle of charity Parfit employs in interpreting Williams, we find decisive reason to interpret Mackie as using the same normative concepts as Non-Naturalists.