Abstract

My thesis demonstrates that, despite a number of impossibility results, a satisfactory and coherent theory of population ethics is possible. It achieves this by exposing and undermining certain key assumptions that relate to the nature of welfare and personal identity. I analyse a range of arguments against the possibility of producing a satisfactory population axiology that have been proposed by Derek Parfit, Larry Temkin, Tyler Cowen and Gustaf Arrhenius. I conclude that these results pose a real and significant challenge. However, in the absence of further evidence I reject the conclusion that they imply that the value of populations is either not precise or not transitive. Instead, I expose some fundamental assumptions behind these results. One key assumption is that something can only make a life better or worse if it makes that life better or worse for the person living it, i.e. it raises or lowers the ‘welfare level’ of that life. Although intuitively highly plausible, this assumption ignores the possibility that perspectives other than that of the person living a life may be relevant for evaluating the components of that life and that these should be incorporated into our all things considered judgements. I argue that episodes within a person’s life that are strongly psychologically connected may have a special normative significance, particularly if these episodes involve such things as the enjoyment of ‘the best things in life’ or the experience of great suffering. We have reason to assign an all things considered value to such strongly psychologically connected phases of a person’s life, where this value is not exhausted by the contributions these make to the welfare level of that person’s life as a whole. It follows that our all things considered evaluations of populations are often underdetermined by information about the welfare levels of the lives they contain. However, in certain cases, most notably in that of ‘the Repugnant Conclusion’, there is nevertheless sufficient information provided by the welfare levels of persons’ lives to allow us to infer facts about these components that make an all things considered difference to these evaluations. I argue that a failure to acknowledge these facts is the cause of the aforementioned impossibility results and that once they are taken into account it is possible to produce a satisfactory theory of population ethics.