Further dilution of marriage could have dire results

American advocates of gay marriage often say that those who oppose gay marriage are no different to those who opposed the repeal of the anti-miscegenation laws, that is, the laws forbidding marriage between blacks and whites.

The reasons for opposing gay marriage, they say, are just as spurious as those of the racists were. This argument is likely to make those who oppose gay marriage, or even those who just feel uneasy about it, feel as if they have been punched in the stomach. It is horrible to think one's opposition might be simply based on ancient prejudice, or an appeal to a fundamentally unjust tradition.

Yet is it a fair analogy? Is the argument against gay marriage much more about the nature of marriage than it is about being gay? When it comes to marriage, is gender a more fundamental barrier than race? Laws regarding inter-racial marriage had to be invented in order to circumvent the reality that black men and white women, and white men and black women would meet, fall in love, marry, and more likely than not, have children. The laws were designed to prevent marriage, not to protect marriage. They were designed to protect white supremacy. Race is an incidental when it comes to marriage, so incidental that laws had to be introduced to prevent inevitable marriages.

Is gender also an incidental, or is it fundamental to the nature of marriage? Whether gay marriage is a good or bad idea does not come down to gay rights, but to this question. Is it merely a strange biological accident that it takes a man and a woman to make a child, and that by and large children thrive if they are reared by the two people who have that biological connection to them? Society has always had an interest in seeing that a couple who have a child are committed to each other and their children.

Marriage far pre-dates Christianity or any institution bearing any resemblance to the modern state. Although it has taken widely diverse forms, from monogamy to polygamy, to the much rarer polyandry, it has always concerned the union of members of the opposite sex. The reason was simple. No matter what shape or form marriage took, it had at its heart the need to protect children, because of the extreme vulnerability of human offspring. Compared to other species, human children are very high maintenance.

They remain helpless and dependent for years. Society privileged the bond that leads to the generation of children, and sought to maximise the likelihood that the biological parents of a child would stay together, because that represented the best chances of survival for a child, and added significantly to the stability of society.

Yet an appeal to history and tradition is not enough, because marriage has constantly evolved to meet the needs of changing societies. It is not so long since marriage was primarily about inheritance, for those lucky enough to have land or property. It is an even shorter time since marriage was primarily a licence to have socially-sanctioned sex, quaint as that notion may seem today. If marriage has constantly evolved, is it sufficiently flexible to evolve beyond any need for it to be between members of the opposite sex?

The erosion of this idea of marriage , whatever its flaws, that had children firmly at the heart of it, has come from the heterosexual community, not from gays. The duty-based and child-focused nature of marriage has given way to an understanding of marriage that is primarily about the emotional fulfilment of adults. No longer to be undertaken until "death do us part," it has become a conditional attachment, to be severed when "my needs are no longer being met".

The link between child-rearing and marriage has been greatly weakened, although the majority of children are still conceived and reared in intact marriages. However, the growing phenomenon of marriages that are childless by choice is alarming demographers, who believe that we are not reproducing frequently enough to sustain ourselves. If, however, heterosexuals can embrace voluntary infertility, why cannot gay people be accorded the benefits of marriage? Western society appears to have decided that marriage is about the personal fulfilment of two people. There is no logical reason, if that is the model of marriage, to deny marriage to people who are of the same gender.

Yet the question has to be asked, whether the erosion of the understanding of marriage as fundamentally child-centred has been valuable, and the rise of the "personal fulfilment model" has been an unconditional good?

Of course marriage should be fulfilling, and a close loving relationship. But can it survive if that is all that it is? Is there something about the yin and yang of relationships, the fundamental differences between men and women, that provides the best environment to raise a child? Of course many marriages are far from perfect - but does that justify passing legislation that declares that either mothers or fathers are not relevant to the development of children, and that two mothers or two fathers are a suitable substitute?

Marriage as an institution, thanks to heterosexuals, has been seriously weakened. If further dilution would amount to a de facto abolition of marriage, do we have any idea what the consequences for society would be? Put another way: would anything be lost, if legislation were passed to declare that the word lesbian henceforth would be simply a word that applied to females, no matter what their sexual orientation? Certainly, something would be gained. It could no longer be a term used in any way to discriminate. It would emphasise what all women had in common, rather than what divides them. What, if anything, would be lost?

Given that sexual orientation is more than a casual accident, a certain precision of language and the ability to describe accurately an important difference would be lost. Is marriage, as a term and a reality, sufficiently flexible to accommodate simply referring to any loving relationship that has some possibility of permanency? Or will something central be lost? I, for one, believe that it will. Racists were wrong to pass laws that inserted something irrelevant to marriage as an impediment to marriage. It would also be wrong to pass laws that say that something fundamental to marriage is irrelevant.