 Kaplow and Shavell’s argument for the exclusivity of welfarism as an evaluative criterion rests on a third leg. The argument contends that use of any non-welfarist criterion is incompatible with the Pareto criterion. Section 6.2 accepts this claim for purposes of argument. The discussion then points out that the Pareto criterion conflicts with principles of rationality, valuation, liberty, and responsibility that have an equally strong  appeal.[30]  It is thus not clear that we should accept the Pareto criterion and reject these others principles.