Many gay couples want to be allowed to call their union "marriage" mainly because they believe this will give their relation a degree of acceptance that is closer to that given to heterosexual unions. They also believe that marriage connotes a more stable long-term relation, although gay unions have a well-known tendency to dissolve at even higher rates than heterosexual marriages, and that very likely would continue even if their unions are called marriages. The narrowly economic gains from being married are a decidedly minor part of the desire by gays to have their matches called marriages.
For the reasons just stated, one can understand why many gay couples want to be allowed to marry. What I find difficult to understand is why there is so much opposition; for example, I doubt if a referendum legalizing gay marriage would pass in many states. As Posner indicates, allowing gay couples to marry will have little effect on either the attraction or stability of marriages between heterosexuals. I believe this opposition reflects hostility to gays and their unions that can no longer be expressed in other more traditional forms, such as calling them names or harassing them. As a result, the marriage issue has become a rallying point that allows hostility to gays to be hidden behind other reasons.
To be sure, it is a strange way to express that hostility in light of other options that have been allowed to gays that are far more radical. I am mainly thinking of the recent practices of allowing gay couples, married or not, to adopt children, allowing lesbian couples to bear children through sperm supplied by sperm banks, or allowing male gay couples to use their sperm to impregnate women who bear children that a gay couple raises. Although rather few gay couples have children as yet, that practice is a far bigger venture into the unknown than is permitting gay couples to be married. It is still too early to have reliable evidence on the effects on children of being raised by gay parents, but I suspect these effects will be more negative than positive, in part because even married gay couples are likely to dissolve their match at relatively high rates.
I also find it strange that gays having and raising children arouses much less opposition than does polygamy, where several women voluntarily agree to be married to the same man (a far rarer form of polygamy is when several men agree to be married to the same woman). Why should society care if two (or more) women are willing to be married to the same man, especially in an environment where men and women rather than their parents generally make their choices about who to marry? We trust women to make many other decisions that seem strange to others-such as when a twenty year old woman marries a 65 year old man- so what logical grounds are there to disallow several woman voluntarily accepting marriage to the same man? Moreover, since polygamy would increase the demand for women as marital partners-however slightly since polygamy would be very uncommon- the argument that it is a form of exploitation of women is also without foundation.
I have proposed for many years that marriage should be basically a private contract between the men and women involved-they can add a religious ceremony if they so desire. There is no reason why the standard contract should be supplied by the government rather than by market forces. An explicit contract would be compulsory, even if it only has a minimum number of stipulations and rules. Most persons marrying might use such a standard contract, but others would have special provisions, such as the allocation of assets in event of dissolution, responsibilities for housework and other activities, and obligations toward children. The state would set minimum obligations toward children since society has an interest in how children are treated.
Such contracts would be equally available to homosexuals, as they are already in some countries and many states of the United States. These contracts would reduce the role of governments in marital arrangements where they have no special competence or interests- again, aside from the protection of children. It would also eliminate the gay marriage issue since gays would have access to contracts as fully as heterosexuals. It would also allow couples to stipulate in writing any special arrangements they want to see enforced in their unions.
Such contracts are unlikely to replace government determined marital terms in the foreseeable future. So until then, it would be wise to expand the concept of marriage to include homosexual relations, and perhaps polygamy as well.