WHAT precisely is a religion, and does it have to involve worshipping a God? Strange as it may seem, Britain's highest court has been considering that question. A member of the Church of Scientology, Louisa Hodkin wants to marry in that organisation's premises in London's financial district. But the registrar-general of births, deaths and marriages has refused to recognise the building as a "place of worship" under the terms of an 1855 law which provides the basis for religious nuptials. Ms Hodkin's attempts to overturn that decision were rebuffed by a court of appeal, so the case is now being considered by the Supreme Court, with some of Britain's top legal brains weighing in on each side. It's a tough question for any panel of judges, even when one of them, Lord Neuberger, comes from a family of famous rabbis. At stake is a 40-year-old precedent, set when one of Britain's most eminent judicial conservatives, Lord Denning, rejected Scientology's claim to be a religion, and hence to provide an appropriate setting for weddings. In that belief system, he asserted, "there is considerable stress on the spirit of Man, and adherents of this religion or philosophy believe that a man's spirit is everlasting and moves from one human frame to another. But it is still, as far as I can see, the spirit of Man and not God."

The Scientologists, for whatever it may be worth, do claim to acknowledge a Supreme Being but say they have no "set dogma" concerning the Deity.

In the current case, Anthony Lester, a Liberal Democrat peer and leading human-rights barrister, took issue with Lord Denning's argument. Buddhism did not believe in a God and yet it was accepted as a religion, he pointed out. For the Scientologists, whose beliefs and practices were established by the late American science-fiction writer L. Ron Hubbard, the British case is only the latest of a series of legal and political battles to be recognised as a religion and therefore gain the tax and legal benefits which older beliefs enjoy. The outcome of these disputes has varied enormously from country to country. In Britain, the movement has failed to obtain charitable status but it does enjoy tax breaks as a non-profit organisation. America's Internal Revenue Service restored Scientology's tax-exempt status in 1993 after a 25-year battle. The German authorities, judicial and administrative, have treated Scientology with scepticsm; several political parties have banned Scientologists from joining.

Still, there is something peculiar about the highest court in a comparatively secular country mulling over the metaphysical claims of a self-described religion and its entitlement to solemnise matrimony. American courts are generally prevented from delving into metaphysics by the First-Amendment ban on an established church. In many continental European countries this issue would not arise because civil marriage is the only kind recognised by the state. People in such countries can of course enter whatever religious rites and unions they wish, and those rites may be more meaningful for them than any civil procedure. But in the eyes of the secular authorities, it is only the civil marriage that counts.

Might it not be a good idea if the British state also went down that route? It would spare judges from having to turn themselves into theologians; it would protect the integrity of religious beliefs about the nature of marriage; and it would create a level playing-field for all manner of pairs of people who want to spend their lives together.