IN A COUPLE of weeks' time, on 18 September, the residents of Scotland will vote whether or not to leave the United Kingdom (Comment, 2 November 2012, 14 March 2014; Paul Vallely 29 August). One way or another, the outcome will affect all of us on these islands.

The Churches in Scotland have remained officially neutral, readying themselves for the work of reconciliation which will be needed to tackle the bitter disappointment that the referendum's verdict is bound to generate.

Individual Christians, on the other hand, have ranged themselves on opposing sides of the debate. I am among them. As an Anglo-Scot, I am a visceral supporter of the Union between England and Scotland, and an opponent of Scottish separation. I am not impartial. Nevertheless, as a Christian, I have a duty to test my convictions against the moral implications of my faith.

The first thing I have to admit, therefore, is that no nation is guaranteed eternal life. One of the features that distinguishes Christianity from its Jewish parent is its detachment of religious faith from blood and land. This was already evident in Jesus's distancing himself from militant Jewish nationalism and from the Temple cult in Jerusalem, and in his recognition of genuine faith on the part of the Samaritan woman at the well, and of Roman centurions.

It found its mature expression, however, in St Paul's mission to the Gentiles, which involved statements such as the famous one in Galatians 3.28: "There is no longer Jew or Greek . . . for you are all one in Christ Jesus."

So Christians may not buy into the idolatrous Romantic nationalism that divinises nations and accords them an eternal destiny. In Christian eyes, nations come and go, rise and fall. The United Kingdom did not exist before 1707. The United States could have ceased to exist in the early 1860s. Czechoslovakia did cease to exist in 1993.

It might be, therefore, that the UK has come to the end of its natural life, and that it is time to dismantle it. That is a conclusion that I would not welcome; but I acknowledge that it might be the right one.

THE strongest justification for Scotland's separation would be that it has suffered some grave and chronic injustice, for which remedy has long been sought, but never found. But it has not. In the Union, Scotland has always been somewhat autonomous, retaining its own Church, law, and education system.

Since the Scottish Parliament was established in 1999, the Scots have enjoyed representation both in Edinburgh and in London. In the UK, they receive more public spending per capita than the English, and, whatever strikes visitors to Scotland today, it is not a signal lack of cultural vitality.

The strongest argument that supporters of separation use is that the Scots prefer a left-of-centre, social-democratic polity with a more generous welfare state, whereas, judging by its propensity to elect Conservative governments, the English electorate's centre of gravity is markedly further to the Right, and more favourable to the free market. As a consequence, the Scots' legitimate aspiration for a fairer, more equal society has been consistently stymied by a neo-liberal Westminster.

If this were true, it would certainly be a reason for greater Scottish autonomy, and a further devolution of powers from Westminster to Edinburgh, although not necessarily for outright secession from the UK. As it happens, however, the narrative of nationalist politicians does not tally with the hard evidence of the social-scientific data, which suggests that, overall, the Scots stand only very slightly to the left of the English.

ANOTHER plank in the Yes campaign's platform comprises the claims that membership of the UK inhibits Scotland's economic growth, and that an independent Scotland would have a higher standard of living.

These claims depend for their truth on a number of variable and (in the crucial matter of the price of oil) volatile factors. They are also highly speculative and fiercely contested. As has been witnessed in the past 12 months, economic claim is matched with counter-claim.

What is clear is that it is not certain that independence would make the Scots better off economically; that there is no reason to be confident that it would make them dramatically wealthier; and that there is some reason to fear that it would actually make them poorer.

One recurring theme in nationalist talk is the vision of a Scottish future purified of the taint of oppressive empire and of aggressive foreign policy. Thus Alex Salmond has written of Scottish independence as a happy surrender of Britain's post-imperial delusion about global influence.

In my view, this would involve a retreat from international responsibility into a narcissistic backwater, leaving someone else (presumably the United States) to shoulder the burden and take the risks of global policing. As a former Scottish National Party candidate commented last year: "The SNP hasn't got a foreign policy, apart from being nice to everybody."

Quite what benefits independence would bring to Scotland remain elusive. There is no certainty that it would make her much wealthier. There is no reason to think that the Scots would use their new-found sovereignty to create a significantly different balance between free enterprise and public provision.

They are already enjoying an upsurge in cultural vitality and confidence. And the movement toward a more "Nordic" defence and foreign policy would be a retreat from responsibility in international affairs.

So my main objection to Scottish independence is that it is really not clear what problems it would solve, or what good it would do the Scots. It seems to me that Scottish independence is a solution in search of a problem; a faith that fails to marshal persuasive reasons.

WHILE the alleged benefits of Scottish independence lie somewhere between uncertain and irresponsible, the costs and risks will be higher than Mr Salmond likes to pretend. The international standing and power of the remaining UK would be bound to suffer, and the risk of a serious souring of relations between the Scots and the English is high.

It is quite true that the Scots alone can choose to separate, but the Scots alone could not dictate the terms of separation. Another party would be involved, with its own interests to look after. And it is stretching optimism way beyond credibility to pretend that the interests of a separating Scotland and the remaining UK would be identical.

It is a practical certainty, therefore, that the separating Scots would not get all that they want; that they would be frustrated; and that their traditional resentment of England would only deepen.

At the same time, most English (and Welsh and Northern Irish) people would feel spurned by a Yes vote; find their own national identity hardening against the Scots; and be seriously disinclined to play patsy. How far the "social union" between the Scots and the British would survive post-vote wrangling is anyone's guess. But no one with their eyes open can presume that the high degree of trust that we now take for granted would survive intact.

As it now stands, therefore, Scottish independence seems to me to be a fetish, which its worshippers credit with the magical power of conjuring up the panacea to all of Scotland's ills. But a fetish is a false god, and faith in it is a faith without reason, which is destined for disillusionment.

The Revd Dr Nigel Biggar, a native of Kirkcudbrightshire, is Regius Professor of Moral and Pastoral Theology, and Director of the McDonald Centre for Theology, Ethics, and Public Life at the University of Oxford.