¹ I take heed of the clause ‘in most circumstances’. Sometimes, obligations to friends, neighbors or fellow citizens are undeniably intense and life-altering (e.g. in wartime), and some obligations to other family members are more demanding (e.g. in the case of a family member who needs long-term care for a protracted illness or disability). Nevertheless, we typically provide more care, more intensively, and for a longer period for our children than for anyone else in our lives.

² See, Torgovnik, Jonathan, Intended Consequences: Rwandan Children Born of Rape (New York, 2009)Google Scholar.

³ Dworkin, Ronald, Law's Empire (Cambridge, MA, 1986)Google Scholar.

⁴ See Card, Claudia, ‘Against Marriage and Motherhood’, Hypatia 11 (1996), pp. 1–23CrossRefGoogle Scholar. See also, Kolodny, Niko, ‘Which Relationships Justify Partiality? The Case of Parents and Children’, Philosophy & Public Affairs 38 (1) (2010), pp. 37–75CrossRefGoogle Scholar.

⁵ This may be entirely unreasonable. Yet, those who believe that abortion is unacceptable even in the case where a mother's life is at risk hold such a view. Outside of the question of the morality of abortion, it is probably not uncommon to think that a parent ought to give her own life if forced to choose between herself and her child.

⁶ Scheffler, Stephen, Boundaries and Allegiances (Oxford, 2001), pp. 56–7Google Scholar.

⁷ These questions have been thoughtfully addressed by Brighouse, Harry and Swift, Adam, ‘Legitimate Parental Partiality’, Philosophy & Public Affairs 37 (2009), pp. 43–80CrossRefGoogle Scholar, and by Kolodny, ‘Which Relationships Justify Partiality?’.

⁸ This is compatible with thinking that we have filial obligations. It is just to say that a parent is prima facie obligated to care for her child independently of whether the child will meet his own filial obligations. Further, the care is largely temporally and epistemically distinct; the parent must provide the care without knowing how she will be cared for in the future.

⁹ Dworkin, Law's Empire, pp. 199–200.

¹⁰ There is a substantial literature documenting parental (particularly maternal) ambivalence. As an example, see Adrienne Rich's influential account of motherhood (Rich, Adrienne, Of Woman Born: Motherhood as Experience and Institution, (New York, 1986), pp. 13–14Google Scholar, 32–3). There is also evidence that parental ambivalence and infanticide are human universals given certain environmental or cultural conditions. See, Davis, Jennifer Nerissa and Daly, Martin, ‘Evolutionary Theory and the Human Family’, The Quarterly Review of Biology 72 (1997), pp. 407–35CrossRefGoogle ScholarPubMed, at 430. See also Hrdy, Sarah Blaffer, ‘The Past, Present, and Future of the Human Family’, The Tanner Lectures on Human Values 23 (2002), pp. 57–110Google Scholar.

¹¹ See McPherson, Lionel, ‘The Moral Insignificance of “Bare” Personal Reasons’, Philosophical Studies 110 (2002), pp. 29–47CrossRefGoogle Scholar.

¹² This is a variation of an example used by McPherson, ‘The Moral Insignificance of “Bare” Personal Reasons’, esp. p. 38.

¹³ Intuitively, the bare relation matters more, in terms of obligation, as it goes from parent to child rather than from child to parent. While I don't think that an account of parental obligation and an account of filial obligation should parallel one another (as will be clear in this article, I think they clearly have different justificatory grounds), I do think it is telling that we probably wouldn't regard bare biological relation as a good enough reason to care for one's parents. If the bare biological relation is insufficient in this case, it is likewise insufficient for the case of parental obligation.

¹⁴ McPherson, ‘The Moral Insignificance of “Bare” Personal Reasons’, pp. 32–3, emphasis added.

¹⁵ McPherson, ‘The Moral Insignificance of “Bare” Personal Reasons’, p. 47.

¹⁶ How to quantify over this conclusion is an empirical matter that is not easily resolved. The factors to take into consideration include the circumstances mentioned above, but also societies where mothers have diminished power in the family structure, where there are religious or cultural forces constraining a person's reproductive life, and perhaps even where a person does not choose her spouse. Each of these factors mediates the voluntariness of parenthood to different degrees, and they interact with one another to create complicated constraints on the causal control a parent has over reproduction. Here, I am making the normative claim that they do in fact diminish a parent's obligation toward a child. The further empirical question is how many parents have such a diminished obligation if the normative claim is correct. My suspicion is that it will be the majority of mothers worldwide, although not necessarily the majority of all parents.

¹⁷ The true analysis of this conflict is much more complicated and may depend on factors such as the perceived quality of the offspring, whether paternity is shared between offspring, the needs of other children (e.g. how close they are in age), and possible conflicts in genetic expression between both genetic parents. See Trivers, Robert, ‘Parent–Offspring Conflict’, American Zoologist 14 (1974), pp. 249–64CrossRefGoogle Scholar; Haig, D., ‘Placental Hormones, Genomic Imprinting, and Maternal-Fetal Communication’, Journal of Evolutionary Biology 9 (1996), pp. 357–80CrossRefGoogle Scholar.

¹⁸ Unlike other animals, humans are not uniform in our care of children. We don't always gobble up the placenta, lick our babies, or build nests. Unlike many other primates, we sometimes abandon our sick or disabled babies, and we don't always protect them from abuse by unrelated adults. We don't always choose to care for them in difficult environmental conditions, and we don't always mourn their deaths. We also differ from most other primates in that we sometimes space our babies too close together, accepting that some of them will die.

¹⁹ For much of this section I am indebted to the research and accompanying scholarship of Sarah Blaffer Hrdy. In particular, see Mother Nature (New York, 1999) and references therein.

²⁰ Hrdy, Mother Nature, p. 131.

²¹ Hrdy, Mother Nature, pp. 138–9.

²² Hrdy shares the following stark anecdote about rats: ‘A virgin female rat . . . will either ignore or devour a pup she happens upon. But if she is repeatedly exposed to pups, this inexperienced “au pair from hell” becomes quite nurturing – without undergoing the hormone changes specific to pregnancy. When experimenters place pups in her cage again and again, eventually she stops killing and begins to care for them . . . In a now classic experiment, blood from a rat who had just given birth was injected into a virgin female. The transfusion caused a dramatic reduction in the amount of time it took this virgin to retrieve babies. Within fifteen hours, virgin females spontaneously gathered up babies without requiring long, often gory, prior exposure’ (Hrdy, Mother Nature, p. 151).

²³ The medical literature on this topic has grown considerably in recent years. See Caspi, Avshalom et al. , ‘Moderation of Breastfeeding Effects on the IQ by Genetic Variation in Fatty Acid Metabolism’, Proceedings of the National Academy of Sciences 104 (2007), pp. 18860–5CrossRefGoogle ScholarPubMed; Cunningham, A. S., ‘Breastfeeding: Adaptive Behavior for Child Health and Longevity’, Breastfeeding: Biocultural Perspectives, ed. Stuart-Macadam, P. and Detwyler, K. A. (New York, 1995), pp. 243–63Google Scholar; Horwood, L. J. et al. , ‘Breast Milk Feeding and Cognitive Ability at 7–8 Years’, Archives of Disease in Childhood: Fetal and Neonatal Edition 84 (2001), pp. F23–F27CrossRefGoogle ScholarPubMed; McDade, T. W. and Worthman, C. M., ‘The Weanling's Dilemma Reconsidered: A Biocultural Analysis of Breastfeeding Ecology’, Journal of Developmental Behavioral Pediatrics 19 (1998), pp. 286–99CrossRefGoogle ScholarPubMed; Lee, P. C., ‘The Meanings of Weaning: Growth, Lactation, and Life History’, Evolutionary Anthropology 5 (1996), pp. 87–93.0.CO;2-T>CrossRefGoogle Scholar; Oddy, W. H., ‘Breastfeeding Protects Against Illness and Infection in Infants and Children: A Review of the Evidence’, Breastfeeding Review 9 (2001), pp. 11–18Google Scholar; Quinlan, Robert, Quinlan, Marsha, and Flinn, Mark, ‘Parental Investment and Age at Weaning in a Caribbean Village’, Evolution and Human Behavior 24 (2003), pp. 1–16CrossRefGoogle Scholar; Sellen, D. W., ‘Comparison of Infant Feeding Patterns Reported for Nonindustrial Populations With Current Recommendations’, Journal of Nutrition 131 (2001), pp. 2707–15CrossRefGoogle ScholarPubMed; Vestergaard, M. et al. , ‘Duration of Breastfeeding and Developmental Milestones during the Latter Half of Infancy’, Acta Paediatrica 88 (1999), pp. 1327–32CrossRefGoogle ScholarPubMed.

²⁴ See Quinlan, Quinlan, and Flinn, ‘Parental Investment and Age of Weaning in a Caribbean Village’.

²⁵ See Deater-Deckard, K. et al. , ‘Maternal Warmth Moderates the Link Between Physical Punishment and Child Externalizing Problems: A Parent-Offspring Behavior Genetic Analysis’, Parenting: Science and Practice 6 (2006), pp. 59–78CrossRefGoogle Scholar. See also, Simpkins, S. D. et al. , ‘Mother–Child Relationship as a Moderator of the Relationship between Family Educational Involvement and Child Achievement’, Parenting: Science and Practice 6 (2006), pp. 49–57CrossRefGoogle Scholar.

²⁶ See, Davis and Daly, ‘Evolutionary Theory and the Human Family’.

²⁷ See Hrdy, Mother Nature and Mothers and Others: The Evolutionary Origins of Human Understanding (Cambridge, 2009) and references therein.

²⁸ There are exceptions among other animals (e.g. an adult dog raising a litter of kittens), but these are true exceptions and are in no way typical of the species. However, the issue of how it is that social animals may help unrelated members of their own species or members of another species is a complicated one; Hrdy's Mothers and Others provides an introduction to some of the research and literature on this topic.

²⁹ On this see: Daly, M. and Wilson, M., ‘Violence against Stepchildren’, Current Directions in Psychological Science 5 (1996), pp. 77–81CrossRefGoogle Scholar. There is research to suggest that stepfamilies are less stable with each child that is not biologically related to the parent, and more stable with each child that is. More to the point, there is a body of cross-cultural evidence that suggests that stepparents tend to invest in stepchildren less than in biologically related children. Correlatively, child abuse and – in the rare cases in which this occurs – the murder of a child are far more likely to be perpetrated by stepparents. Davis and Daly, ‘Evolutionary Theory and the Human Family’, and reference therein.

³⁰ There is also reason to believe that children who live with stepparents, distant relatives, or non-relatives are more likely to experience stress and a depressed immune system. Flinn, Mark and England, Barry, ‘Childhood Stress: Endocrine and Immune Responses to Psychosocial Events’, in Social & Cultural Lives of Immune Systems, ed. Wilce, J. M. (London, 2003), pp. 107–47Google Scholar.

³¹ Large-scale experiments with wet-nursing as in eighteenth-century France were particularly disastrous and lethal to the babies involved. The social complexities of Europe during this period led to extremely high levels of wet-nursing and the sending of children to foundling homes despite the known risks involved (90 per cent of children failing to survive in some cases). Some have read the history of this period in Europe as well as other cases of endemic child abandonment as clear evidence that maternal love, instinct and affection are not universals, and that they are instead social constructions, or patriarchal impositions. I think this is probably the wrong way to interpret these periods in history. Maternal responses in these cases were probably exceptional responses to the social and environmental constraints of the time. However, terms such as ‘maternal love’ and ‘maternal instinct’ are worthlessly vague. I do not rely on them in this article. See Hrdy, Mother Nature; Kertzer, David, Sacrificed for Honor: Italian Infant Abandonment and the Politics of Reproductive Control (Boston, 1993)Google Scholar; Trexler, Richard, ‘The Foundlings of Florence’, History of Childhood Quarterly 1 (1973), pp. 259–84Google Scholar; Boswell, John, The Kindness of Strangers: The Abandonment of Children in Western Europe from Late Antiquity to the Renaissance (New York, 1988)Google Scholar.

³² I would like to acknowledge the assistance of the editors of this journal and two anonymous referees for their helpful comments in revising this article. I am also especially grateful for the extensive assistance provided by Michael Tiboris and Cory Wright on earlier versions of this article.