How to avoid the repugnant conclusion

Derek Parfit thought that his continuum argument in population ethics leading to the Repugnant Conclusion—viz., that a world with a vast number of people leading lives barely worth living is better than a world with many people enjoying excellent lives—raised a puzzle that must be solved before we can hope to arrive at a correct theory of morality, what he called ‘Theory X’. This chapter critically examines four possible ‘structural’ solutions to continua arguments like Parfit’s—solutions according to which the structure of continua is not as continua arguments suppose. It is argued that incommensurability, incomparability, indeterminacy, and indeed Parfit’s own preferred solution, ‘lexical imprecision’, fail to provide the break in structure needed to defuse continua arguments. An alternative structural solution is then proposed according to which, somewhere along the continuum, items are on a par with their immediate predecessors. Being on a par is a sui generis fourth basic way two items can be compared beyond being better or worse than one another or equally good. The parity solution is shown to have two significant advantages over the other structural proposals. First, only the parity solution allows us to maintain the very plausible thought at the heart of continua arguments, viz., that as we proceed along the continuum, a small diminution in quality of value can be compensated for by a large increase in quantity of value. Second, by appealing to a tetrachotomous, rather than a trichotomous, view of value—a view of value that includes parity—we can vindicate first-blush, untutored, intuitive reactions as to what goes wrong in continua arguments. Thinking about what some may have too readily dismissed as a ‘mere puzzle’ opens up new ways of thinking about the very structure of normativity and the shape of Theory X