Making a vague difference: Kagan, Nefsky and the Sorites Paradox

Abstract

ABSTRACT In collective harm cases, bad consequences follow if enough people act in a certain way even though no such individual act makes a difference for the worse. Global warming, overfishing and Derek Parfit’s famous case of the harmless torturers are some examples of such harm. Shelly Kagan argues that there is a threshold such that one single act might trigger harm in all collective harm cases. Julia Nefsky points to serious shortcomings in Kagan’s argument, but does not show that his conclusion is incorrect. I argue that our best theories of vagueness (the epistemic view of vagueness, three-valued logic, and supervaluationism) entail that there is a threshold in all collective harm cases. However, my analysis points to another problem with Kagan’s argument: the thresholds are not necessarily perceptible. Given the assumption that only perceptible differences matter morally, passing such a threshold does not necessarily trigger morally relevant harm, pace Kagan. Last, I consider two variants of Kagan’s argument and find both problematic. One controversially assumes that observational relations like ‘cannot perceive the difference between’ are transitive. The other problematically assumes that so called triangulation always is possible.