 Epiphenomenalists can be expected to deny the necessity of causal relations for individuation. They may consistently hold, for example, that the unique hues are qualities that simply differ and have no metaphysical need for a principle of individuation. An epistemological problem, however, may appear to remain: How can epiphenomenalists know that they experience different phenomenal qualities? This, however, is the self-stultification problem in a different guise, and epiphenomenalists can refer to the responses already considered.