Stephen J Gould famously argued that science is not in conflict with religion because it answers a different kind of question. The two are non-overlapping magisteria. Science says nothing about the Trinity, and religion says nothing about the photoelectric effect. This view is not universal: Richard Dawkins argues in The God Delusion and elsewhere that science does speak about religious claims and says that they are false.

But does the concept of non-overlapping magisteria apply to religion and politics? Perhaps not historically, but since Catholic Emancipation, since Charles Bradlaugh was permitted to take his seat in the House of Commons as an atheist, we have enjoyed a happy situation where religion does not divide us politically, nor vice versa.

This is perhaps surprising. Religion and politics are both in the values business, most politicians are religious and are inspired by their faith to work through their politics. Why then aren't the Labour Party Catholic, the Conservatives Anglican, the Liberal Democrats non-conformist, the Greens Buddhist, Respect Muslim? Of course these influences do exist at least a little, but we have learned from bitter experience, from Cromwell the puritan, Northern Ireland, and elsewhere that it does not make for social cohesion or good politics for religious and political allegiances to coincide. We have instead a political culture that people of any faith and none can participate in equally. Or at least we aspire to that.

Is this culture beginning to break down? Does the principle that faith or lack of it should be no barrier to any office mean that there should be no objection to having a member of Opus Dei responsible for anti-discrimination policy? (Links: Mayor Watch, Lib Dem Voice, The Labour Humanist, Millennium Elephant)

Indeed. There should be no objection. My objection is to having an Opus Dei member who agrees with Opus Dei policy in charge of anti-discrimination policy. It should never be assumed that adherents to a faith agree with the political views of their faith leaders, even if those leaders insist that they must.

Religious neutrality is a tremendous asset of our political culture, and it would be madness to abandon it. But concern to maintain this neutrality has perhaps led us to tread too carefully when we should be standing up for our values.

We should not feel obliged to agree with people whose reasons for their political views are religious. If we do, we may find that more and more policy areas will find themselves under the religious banner, and more political debates will become one-sided. Where today it is faith schools and discrimination, tomorrow it will be scottish independence and trade policy.

Some will see this as bringing badly-needed values into politics. But this is missing the point - politics is already about values. We oppose discrimination because it is wrong. We support the health service because curing the sick is good. And politics is already a process by which different values compete. Join in, bring us your values and your arguments, but you are not doing anything different to the rest of us. And you will find people of every faith and none on both sides of just about every political question.

Gould's non-overlapping magisteria represented a desire to avoid a conflict between science and religion that Dawkins would rather not avoid.

Politics and religion overlap big time, and always have done. But when this overlapping is explicit, it can make us uncomfortable. We have avoided a conflict by experiencing that overlap in the minds of individuals, and not in the institutions of faith and politics. For this reason I am particularly wary of Ruthy Kelly's claims to be able to compartmentalise her political duties from her religious beliefs.