The burden of proof, in other words, should be carried by those who oppose legal and moral equality for homosexuals, not those who favor it. Marriage is a pledge of commitment, of a long-term bond, between two people to stay together, to look after each other, to be faithful to one another, to share costs, incomes and assets. To decide to marry is to decide to make an extra, stronger commitment beyond simply stating one's love, or simply living together. I can see no reason why this should be denied to one category of human beings on grounds of their sexual preferences.

Some respond by saying that marriage is, by definition, between a man and a woman. But this is like saying that nothing should ever be changed from its initial state. That old definition is wrong. So it should be changed. Others argue that marriage is there to protect children. Nonsense: that may be a nice side-effect of the institution, but it is not its essential purpose. My wife and I have no children. Does that mean we are not entitled to be married? Of course not.

It is a simple question of equal human rights. If you want to complicate it, then add an argument of social order and practicality: the more committed couples we have in our societies the better. It makes no sense to deny that extra pledge of commitment to people who want to make it. And "civil unions" or other quasi-marital partnerships are not enough. The right outcome is full legal equality.

Read Emmott's cover article from The Economist here: The Case for Gay Marriage.