Although rooted in biological realities, marriage exists mainly as a social convention.
Marriage is historically understood as a union between a man and woman. Efforts to describe just what kind of union reveals its multifaceted character. The most common models understandings include marriage as a social practice, a religious rite, a legal contract, and a civil institution.
First, marriage as a social practice is the most fundamental. As a social practice, marriage precedes political society and the modern state’s establishment of marriage as a legal institution. Marriage brings together a man and woman into a new relationship between them and into a new standing before the larger society. For most of human history and in traditional patriarchal societies today, fathers arrange the marriages of their children. Arranged marriages usually are endogamous in that they maintain existing kinship networks. Marriages between relatives sharing some degree of consanguinity reinforces tribal or clan identity. Of course, families arrange exogamous marriages outside the existing kinship ties as well in order to establish new ones. Enhancing the economic well-being or status of the families motivates many if not most arranged marriages. As a social practice, traditional marriage serves the related functions of regulating sexual behavior, establishing the legitimacy of offspring, and defining property arrangements. Romantic love or passion between spouse either do not constitute a crucial aspect of arranged marriages at all or is expected to emerge during the marriage. The rise of modern romantic marriage, however, fundamentally altered traditional practices. In the West and in other less traditional societies, modern marriage is understood as a matter of individual choice.
Second, because most societies contain one or more religious traditions, marriage is also considered a religious rite. The ceremony informs the event with religious meaning as the couple assumes a new standing before God--however he is conceived. This usually means some religious official presides over the ceremony, confers divine blessings on the union, and provides some sort of theological understanding of marriage within that society‘s religious tradition. Marriage as a religious right endures even in today’s more secular age. In most nations, the state authorizes religious officials to conduct marriages.
Third, because marriage involves some agreement between parties, whether between family heads in an arranged marriage or between individuals in modern marriage, it is also described as a contract. In fact, most civil codes today define it as such. When a proposal for marriage is agreed upon, the couple exchanges promises regarding rights and duties. Marriage differs from other legal contracts, however, in that the parties rarely write out the rights and duties as clauses in a formal agreement. The modern state has assumed regulatory powers over marriage through licensing. The state establishes licensing procedures and specifies who may enter into marriage contracts and what kinds of marriage contracts it will recognize. The state accords recognition based upon the interests of the state.
That last point is the essential one the in current debate about same sex marriage. Few people oppose, or at least possess any standing to oppose, a same sex marriage ceremony conducted in some liberal mainline church or Las Vega wedding chapel. Any same sex couple has the freedom to walk an aisle, make mutual pledges of love and fidelity, and declare to their friends that they are now . . . well, spouse and spouse.
The point of debate is whether or note states lie under any moral or legal obligation to recognize such unions.