Abstract

In his book Reasons and Persons, Derek Parfit proposes the search for a self-consistent theory of population ethics, a theory capable of answering questions about the welfares of populations in a manner that satisfies all of our ethical intuitions, what he calls “Theory X.” But in the same work, Parfit offers what he sees as a major obstacle to that goal, the so-called “Repugnant Conclusion”, worrying whether the most well-off population is an increasingly large population. This problem, along with Roderick Ninian Smart’s “Negative Utilitarianism” and Robert Nozick’s “Utility Monster” belong to a special class of ethical cases dealing with the mathematical limits of zero and infinity: trivial and unreal ethical solutions. These kinds of problems have plagued population ethics since Thomas Malthus first recognized the problem of exponential growth and its deleterious effects on personal wellbeing. In an attempt to answer Parfit, some, such as T. Sider, T. Hurka, and Y. Ng, have suggested formulations of marginal wellbeing without undermining core ethical principles. Other authors, like G. Arrhenius et al., have suggested that Parfit’s problem fundamentally undermines the possibility of a self-consistent population ethics. Here we will suggest that these problems result from an improper inclusion of trivial and unreal numbers into the ethical domain, making what Parfit calls “mistakes in moral mathematics,” and are thus resolved by an exclusion of trivial and unreal numbers from the ethical domain by carefully specifying a welfare function to exclude them.