The 'debate' about gay marriage is a dialogue of the deaf. Perhaps economics can help. The solution is to trade.

Right now, gays don't have a right to marry. But they could, in theory, buy it. They could pay religious organizations to drop their objections. If the right to marry is more valuable than believers' hostility to gay marriage, both parties will find a price at which the right to marry can be bought. If, on the other hand, gays don't value the right as highly as believers value its prohibition, they'll not agree a trade, and so they won't get the right.

For example, say that in a society of 100 people six gays would pay ''1000 each for the right to marry, and that there are 20 people who find the thought of gay marriage abhorrent, with the rest of the society indifferent. Let's say the discomfort of those 20 people has a monetary value to them of ''100. Then their discomfort could be bought out, as 6 x ''1000 more than pays off 20 x ''100. If, on the other hand, the 20 people's discomfort has a monetary value of ''500, gays would be able to buy the right to marry.

Now, you might object that the present status quo should not be the default position, but that gays should have a right. No problem. We could start from this position and then ask believers to buy out gays' right to marriage. If they value their objections to that right by more than gays value their right to marriage, then they'd agree a price at which the right to marry could be forfeit.

In theory, under some assumptions, it doesn't matter where we put the right. Trade will ensure that gays get the right to marry if they value the right by more than others value the prohibition.

What I've just described is the Coase theorem. My thinking was triggered by ch 7 of Robert H Frank's The Darwin Economy.

There are three objections here:

- Contrary to Coase, the original position does matter. People value the status quo. So asking gays to buy the right to marry and asking believers to buy its prohibition are not equivalent.

- Asking people to pay does not reveal the value of the right so much as the value of money. It gives undue power therefore to the wishes of the wealthy.

- There are terrible transactions costs and free rider problems involved here, in getting gays and believers to club together.

These objections, though, don't matter. The point is that the location of the right should go to where it would if free and efficient trading were feasible.

This principle applies to the rights we actually have. The reason why I have a right to life is that I would pay more for that right than others would pay to kill me. A similar thing is true for rights to, say, free speech, association or religious belief.

I suspect that this principle would give gays a right to marry; I say this simply because heterosexuals value marriage so highly that they pay fortunes for ceremonies, and I suspect a similar thing would be true for many gays.

But this is not the point. The point is that economics can help find ways of solving problems that otherwise seem intractable; everything I've said also applies to abortion rights.

And herein lies a paradox. I suspect that many of the participants on either side of the argument about gay marriage or abortion have something in common. Many liberal lefties and religious believers are sceptical about free markets, believing that they encourage an individualism that erodes social cohesion. In this case, though, the use of markets - if only as a thought experiment - can bring people together and create social cohesion whilst it is strident statements of religious or egalitarian ideology that weaken social ties.