Abstract

Derek Parfit's combined-spectrum argument seems to conflict with epistemicism, a viable theory of vagueness. While Parfit argues for the indeterminacy of personhood, epistemicism denies indeterminacy. But, we argue, the linguistically based determinacy that epistemicism supports lacks the sort of normative or ontological significance that concerns Parfit. Thus, we reformulate his argument to make it consistent with epistemicism. We also dispute Roy Sorensen's suggestion that Parfit's argument relies on an assumption that fuels resistance to epistemicism, namely, that 'the magnitude of a modification must be proportional to its effect.'