 Can prospective children be said to have an interest that their parents not act in a way likely to lead to their birth when the parents are in a position to know that the life of the child, should it be born, would fall below some relevant threshold of well-being? (On the significance of the notion of a threshold level of well-being, see below,  §3  and  §4).  John Stuart Mill endorses the idea of a procreational duty of omission, namely, not to bring a person into existence unless the person will have “at least the ordinary chances of a desirable existence” (see Mill 1859 [1977: 301–304]). It is a widely held belief that under certain circumstances prospective parents should refrain from procreating owing to the predicted plight of the would-be child. Antinatalists hold that these conditions hold generally (see, e.g., Schopenhauer, 1851: vol. 2, ch. xii, § 149; Cioran, 1978: 117; Horstmann 1983: 99–101). More recently, for example, Seana Shiffrin (1999) and David Benatar (2006: esp. ch. 2) have argued that causing someone to exist always entails the frustration of some of the person’s interests and nontrivial harm to that person, and therefore we ought to refrain from procreating.