I am grateful to Holly Smith, Walter Sinnott-Armstrong, and an anonymous reviewer (who suggested the questions in the conclusion) for helpful comments, and to a number of people for literature suggestions, especially Michael McCullough. Work on this entry was supported by a grant from the Templeton World Charity Foundation. The statements made here are those of the author and are not necessarily endorsed by the Templeton World Charity Foundation. Material from sections three and four draws from Miller 2015.