The Self-Undermining Arguments from Disagreement

Arguments from disagreement against moral realism begin by calling attention to widespread, fundamental moral disagreement among some group—ordinary people, moral philosophers, idealized agents—and draw a skeptical or anti-realist conclusion. I argue that all such arguments share a structure that makes them vulnerable to a single powerful objection: they self-undermine. In every formulation, at least one premise casts doubt either on itself or another premise. On reflection, this should not be surprising. To derive sweeping metaphysical or epistemological conclusions about morality—for example, that there are no moral facts or that none of our moral beliefs are justified—these arguments require correspondingly strong metaphysical or epistemological premises. But, given the pervasiveness of disagreement in philosophy—especially in metaphysics and epistemology—such premises are almost certain to be the subject of widespread, intractable disagreement: precisely the kind proponents of these arguments claim undermines moral claims. These arguments therefore undermine their own premises. If my argument is sound, it provides realists a single, unified strategy for responding to arguments from disagreement and poses a challenge to any future versions philosophers may advance.