Marriage secures the equal value of men and women One of the goods of marriage is that it confers social recognition on a relationship which is dependent on the gendered 'other'. Thankfully, we live in an age and society which has done more than most to ensure that gender roles are fluid, that men and women are equally able to access jobs, careers and other social opportunities, as well as taking up domestic responsibilities. Yet we still recognise that men and women are in various ways different. The point about equality for men and women is not that the difference is irrelevant, but that both are equally valuable and necessary. We may struggle to identify all the dimensions of that difference, and disagree about their significance, but as many feminist writers have rightly recognised, 'gender-blindness' is not the answer. Gender-blindness runs the risk of entrenching norms and practices which typically favour men and are oppressive towards women. The fact of difference has to be acknowledged and valued if we are to secure equality. That is why we are right to worry about the small number of women MPs or CEOs.
Marriage as currently defined is the central social institution which expresses the idea that men and women are equally valuable as men and women. It is only marriage which harnesses gender difference to the purposes of social cooperation. Almost all other ways in which difference is acknowledged - from sports teams to public lavatories - depend on segregation. Sexual union in marriage reinforces a comprehensive 'together-in-otherness' of male and female. Yet marriage is also open to a wide range of views on the practical outworking of this difference. It would be ironic if after having reformed the patriarchal consequences of marriage the institution itself should become gender-blind.
The grounding of interdependence in marriage has wider social consequences. It anchors our understanding that it is normal for all social institutions to rely on this mutual interdependence. The excessive individualism of modern Western society, as well as the collapse of participation in all forms of organised social action, has often been observed. Redefining marriage to be indifferent to sexual identity reinforces this individualistic tendency because it turns human society - from marriage outwards - into a matter of individual inclination and choice. Marriage will cease to be an institution which reflects the necessary and natural interdependence of men and women. Every successful relationship depends on some degree of mutual dependency, but marriage is distinctive in recognising and valuing a difference that is deeper than those of character and circumstance. The man-and-woman criterion not only secures gender interdependence in marriage, it also models and promotes this gender interdependence more widely across society.
Marriage promotes the welfare of children While the connection between the current definition of marriage and the equal value of men and women is quite clear, the implications for children are less obvious. Marriage and childbearing have become disconnected in historically unprecedented ways. More precisely, childbearing has become a matter of unprecedented choice. The availability of effective contraception makes decisions to avoid childbearing more reliable. Medical advances have increased the possibilities of childbearing for infertile and older couples. Individuals and same-sex couples can now take steps to acquire a child by adoption or by making medical arrangements.
In spite of these developments, there are still connections between marriage as currently defined and the bearing and rearing of children. Most married couples of childbearing age will be able to have children and will have to take steps to avoid having children. By contrast, individuals and same-sex couples have to take active steps to acquire a child, at some point involving another party. Far fewer do. So there is a social and practical presumption connecting marriage with children. But the connections go deeper than this.
A child represents the combined genetic inheritance of his or her parents. She is the embodiment of both, a living testimony to their intimacy and a bearer of the identity of earlier generations. A child is likely to outlive her parents, and so this embodiment symbolises the permanence of marriage as well as its heterosexual nature. We know that these multiple intertwined relationships are important, both on account of the strong natural desire people have to know their genetic parentage as an aspect of their identity, and because of the pain a child experiences on divorce. The child can feel almost literally torn apart. This means that there is a distinction between sexual union and sexual intimacy. A sexual relationship can be called a 'union' not because it is intense, but because it can be embodied in a new human person. Only a man and a woman can form the biological unit capable of pro-creating another being 'free and equal in dignity and rights'. No new human being can exist as a living expression of the intimacy of a same-sex couple.
Redefining marriage to include same-sex partnerships will have two distinct effects. As far as same-sex couples are concerned, it will close off the question of the impact of same-sex parenting on children. But more importantly, it will sever the presumptive connections between marriage, childbearing and kinship for everyone.
As far as the first point is concerned, there is an inconclusive and controversial debate about the impact of same-sex parenting on children. Quite apart from the high political stakes, there are the problems of what one is comparing same-sex parenting with (single parenthood, step-parenthood, institutional care, natural parenting?) and what counts as a negative outcome. Throw in the distorting factors of small sample sizes, social class, education, other disrupting life-events, and the scope for contestation is enormous. The prevailing view is that there is no significant deficit in same-sex parenting, although a recent major study has called this into question. However, we do know that the distinctive gender roles of a father and a mother are important in the psychological development of children. It must be at least possible that having two 'fathers' or 'mothers' will not compensate for the absent mother/father-figure. The data is inevitably recent, and we will not know with certainty for some considerable time what the effects of same-sex parenting are. Recent changes already allow for same-sex partners jointly to acquire children; redefining marriage will render these developments immune from reconsideration. Such confidence seems premature.
But the more important effect is on the place of children within marriage generally. Every child has a moral claim on her natural father and mother, grounded in the fact that they brought her into being and that it is in principle good for every child to be brought up by her natural parents committed in relationship to each other and to her. Redefining marriage breaks the necessary connection with childbearing, in the sense that marriage will no longer mean 'the relationship which is normally and naturally productive of children and thus a nexus of kinship.' Its intrinsic purpose will be reduced to sexually-intimate companionship. And it is bad for children if their parents come to believe that all that being married means is sexually-intimate companionship. Every child needs his or her parents to think of their marriage as embodied in their children. Children benefit from strong wider networks of kinship, not least grandparental care, and it is unrealistic to suppose that these can be created merely by contract. Breaking the intrinsic connections between marriage, childbearing and kinship risks the further commodification of children, in which children become 'ultimate accessories' - means to the ends of their parents, and ultimately subject to their agendas, rather than persons of equal worth, with an equal stake in the success of the marriage.
END PART TWO OF FOUR
 Carol Gilligan, In a Different Voice, Harvard University Press, 1982, was a seminal work. See also Robin West, 'Jurisprudence and Gender', University of Chicago Law Rev.55, 1988, pp.1-72.
 Many historic legal consequences of marriage did not reflect gender equality; but it is the core definition which is now at stake.
 Robert Putnam's 'Bowling Alone: America's Declining Social Capital' (1995) is now a classic study.
 Joint adoption for same-sex couples has been available in the UK since 2005; joint registration after fertility treatment since 2009: ONS, Civil Partnerships Five Years On, Population Trends Nr. 145, Autumn 2011, p.19.
 In 2011, 8.5% of civil partners and 4.8% of cohabiting same-sex couples had dependent children, amounting to 0.1% of all dependent children. ONS, Families and Households 2001 to 2011, January 2012, Table 1. Given the relatively recent introduction of adoption and assisted reproduction, these children are likely to be from previous relationships.
 Of numerous studies of the negative impact of divorce, see the older meta-analysis of 92 studies by Paul R. Amato and Bruce Keith: 'Parental Divorce and the Well-being of Children', Psychological Bulletin 110, 1991, pp.26-46. Judith S. Wallerstein and Julia Lewis, 'The long-term impact of divorce on children', Family Court Review, 36, 1998, pp.368-383, present a focused and qualitative study.
 Universal Declaration of Human Rights 1948, art. 1.
 See the American Psychological Association policy statement on Sexual Orientation, Parents and Children (2004): http://www.apa.org/about/policy/parenting.aspx (accessed 30 August 2012).
 A recent issue of Social Science Research contained a debate on this issue. Loren Marks challenged the reliability of the studies underlying the conventional wisdom: 'Gay and Lesbian Parenting: the State of the Science', Social Science Research, 41, 2012, pp.735-751, and Mark Regnerus presented the findings of the largest survey yet conducted: '[The survey] also clearly reveals that children appear most apt to succeed well as adults - on multiple counts and across a variety of domains - when they spend their entire childhood with their married mother and father, and especially when the parents remain married to the present day.' 'How different are the adult children of parents who have same-sex relationships?', Social Science Research, 41, 2012, pp.752-770. Subsequent expert commentators accept that the research has at least put a question mark against the conventional wisdom, but caution generally against using social science research to solve constitutional questions around same-sex marriage.
 See Christiane Olivier, Jocasta's Children: The Imprint of the Mother, Routledge, 1989, and at a more popular level, Robin Skynner and John Cleese, Families and How to Survive Them, Cedar Books, 1993, ch. 5.
 The right of the child to biological parenting is apparent from the UN Convention on the Rights of the Child (1990), articles 7-9, which contain rights to know and be cared for by both parents, to preserve family identity, not to be separated from parents against their will, as well as a right to maintain personal relations and direct contact even if the parents are separated. Article 3 of the UN Declaration on Social and Legal Principles relating to the Protection and Welfare of Children, with special reference to Foster Placement and Adoption Nationally and Internationally (GA Res. 41/85 of 3 Dec. 1986) states that the first priority for a child is to be cared for by his or her own (i.e. biological) parents.
END PART TWO OF FOUR
Dr. Julian Rivers has contributed regularly to Cambridge Papers for the 20 years of their existence. He has published widely in constitutional law, legal theory, and law and religion studies. He is Professor of Jurisprudence at the University of Bristol Law School, an editor-in-chief of the Oxford Journal of Law and Religion, and a member of the advisory board of the Ecclesiastical Law Journal.