Ethical theory faces a group of difficult puzzles concerning populations. Here is one: would it be right to maximize utility by causing the number of people existing in the further future to be very, very large, even if this means that each of their lives is barely worth living? Derek Parfit concludes that standard utilitarianism yields the result that it would be right to create such a world. He calls this conclusion "repugnant." I begin with an examination of the objection, (...) in which I argue that the problem is axiological, not normative. I present my interpretation of the problem, and consider and reject the most popular and plausible responses in the literature. ;Many people agree with Parfit that the repugnant conclusion is unacceptable. They see this as a strong objection to impersonalism, and conclude that only person-affecting utilitarianism solves the population problems in question. I argue that the most credible person-affecting theories incorrectly answer simple population questions and are deficient in other respects. ;Need we accept Parfit's objection? I advance my own view---that there are totalistic axiologies that do not imply the repugnant conclusion, and defeat the mere addition paradox. I show that these theories have much in common with classical totalism, and they give the intuitively correct result in the crucial cases under consideration. (shrink)