Paul Vallely: Williams is snared in a trap of his own making

Rowan Williams bridles when anyone suggests that he is the Anglican church's equivalent of the Pope. But he has made the same mistake in discussing sharia law that Pope Benedict XVI made in his ill-fated foray on the subject of Islam at the University of Regensburg two years ago, which sparked protests around the world, the murder of a nun and much else.

The error is assuming that the leader of a major church has the same intellectual freedom that he had when he was merely an eminent theologian. The cold fact is that the semiotics are entirely different. An academic may call for a nuanced renegotiation of society's attitudes to the internal laws of religious communities. But when the Archbishop of Canterbury does that the headline follows, as night follows day: "Sharia law in UK is unavoidable, says Archbishop."

This is not what he was saying, and yet it is. News has little room for the subtleties of academic gavottes around delicate subjects. A canny religious leader – or at any rate his press office – ought to know that.

The problem comes when you ask what is meant by sharia. Most of us are clear. It is to do with the stoning to death of adulterous women (even when they have been raped) and chopping the hands off thieves. It is what the Saudis do, and the Taliban.

However, this is, Dr Williams suggests, a travesty of the truth. What sharia means, and most Islamic jurists agree, he tells us, is not a list of laws but a way of thinking that expresses the universal principles of Islam. Codifications of that law, by the Saudis, the Taliban or whoever, are inevitably reductive and therefore false. "An excessively narrow understanding of sharia, as simply codified rules," he says in the full lecture on which the stories were based, "can have the effect of actually undermining the universal claims of the Koran."

What Dr Williams is saying is that we all have overlapping identities. It is possible to be a British citizen, a Muslim, a Tory and a member of the local golf club at the same time. Each of these identities brings with it rules and it is high time that British society took account of this instead of "a secular government assuming a monopoly in terms of defining public and political identity".

Thus, as a golf club or political party may expel a member who breaks its rules, so a religion may have a legal code under which marital or financial disputes can be decided. The law should recognise this, as it does already with the internal systems of Orthodox Jews. But in a way which does not dispense with a citizen's rights to appeal to the courts of law. All but Islamicist "primitivists" would accept that this is a secondary jurisdiction. That, I think, is what he is saying in an immensely dense, 7,000 word text.

The trouble is that most people have not ploughed through all that, which is why the Tories called the Archbishop's remarks "unhelpful", the Liberal Democrats said all must abide by the rule of law and the Home Office minister Tony McNulty said: "To ask us to fundamentally change the rule of law and to adopt Sharia law, I think, is fundamentally wrong."

To all of which the Archbishop may say "but you are objecting to something you think I said rather than what I actually did say". He has a point. But, equally, in a world where perception becomes its own reality, it is important for the leader of the Church of England not to create such fecund opportunities for misunderstanding.