The Repugnant Conclusion is the implication, generated by a number of theories in population ethics, that an outcome with sufficiently many people with lives just barely worth living is better than an outcome with arbitrarily many people each arbitrarily well off. Derek Parfit, who first brought the Repugnant Conclusion to the attention of contemporary philosophers, stated it informally as follows: "For any possible population of at least ten billion people, all with a very high quality of life, there must be some much larger imaginable population whose existence, if other things are equal, would be better even though its members have lives that are barely worth living."^[1]