David Cameron's announcement in a speech last week that the UK remains a "Christian country" made predictable headlines. The speech, delivered during a celebration of the 400th anniversary of the King James Bible, asserted that our culture and politics are incomprehensible apart from a recognition of the Christian heritage of the country, and - most controversially - that the shared values that should guide British politics and society into the future should be distinctively Christian values. 

His first point was relatively uncontentious: there is no doubt that the King James Bible was instrumental (together with the plays of Shakespeare) in creating the cadences of the English language. The second point wandered towards the controversial: "[the] Bible runs through our political history in a way that is not often recognised." 

The examples cited included the concept of a limited, constitutional monarchy; universal human rights; the welfare state; and a commitment to aid and development beyond our borders. I suspect that on each of these examples Cameron was simply right. Even if he is right, however, the fact that the Bible is the source of our original commitment to a constitutional monarchy (say) does not mean that such a commitment can only be based on the Bible. 

The history does establish a burden of proof, however. Public atheism often adopts a series of distinctively Christian ethical - and even philosophical - commitments and asserts that they are in some way 'obvious'. Only a little knowledge of history shows that this is false. It has not generally been obvious to human beings that infanticide is a bad idea, let alone that limited government is a good one. Constitutional monarchies are rare in human history, and generally only adopted by Christian states; if the position can be defended robustly from a naturalistic philosophical position, that requires demonstration. 

The prime minister moved to his third point via a recollection of the importance of faith-based groups in society, and an acknowledgement that, whatever might be happening in Britain, faith is becoming more, not less, important and prevalent globally. Mr Cameron made the choice to welcome this. 

Every strong society, he argued, is built on an unwavering commitment to certain shared values; the values which have shaped, and which should continue to shape, British society are distinctively Christian, although their worth can be recognised by others; therefore a public commitment to Christian values is important and appropriate. Tolerance in particular is a distinctively Christian value, and so a Christian society is better-placed to cope with modern pluralism. 

The remainder of his argument was that faith is a motor for ethics. Reflecting on the banking crisis and the summer riots, he comments that "moral neutrality or passive tolerance just isn't going to cut it anymore". Well, yes, but this assumes that any 'moral compass' is a good 'moral compass,' and that is patently ridiculous. Committed belief in anything tends to creative activists; the moral value of the belief is entirely dependent on the sorts of action it inspires. 

Mr Cameron's argument will be made believable, or rendered ridiculous, by the public lives of Christians in this country. The ways in which we are involved in building and shaping local communities could make the vision of a "Christian country" attractive to our neighbours - or it could make them fear the idea. To do good, and to be known for doing good, is our calling: as Jesus put it, when people see our good works, then they will glorify our Father in heaven (Matthew 5:16)!

Steve Holmes, Senior Lecturer in Theology, University of St Andrews