Statistics don't tell the whole truth, but they can be useful pointers.

St George's Tron, the Glasgow congregation at the centre of the current ecclesiastical storm, had 380 communicants in 2011 and its income (offerings, contributions, investment income, fundraising and so on) amounted to just over £60,000. These figures do not mark it as a particularly large or significant church within the Presbytery of Glasgow (which has 139 constituent congregations), let alone the overall Church of Scotland.

For all that, it may yet have enormous historical significance. It may well be the congregation whose departure from the national church sets in train an unstoppable sequence of events. And it may also be the congregation that alerts the wider Scotland to the fact that its national church can no longer cohere and might, before long, break up.

The above statistics are taken from the Kirk's official yearbook for 2012-13. A perusal of this very informative volume shows that the old, and absolutely crucial, aim of a church and a minister in every parish is now just a chimera. Many parishes – some of them in reality several parishes linked together into an uncomfortable amalgam – are listed with the word "vacant", meaning no minister. So although the national church has, with increasing desperation, been linking parishes, especially in rural areas, there remains an acute shortage of ministers. For secularists, this might be encouraging; for others, it is nothing short of tragic.

Meanwhile the church is bitterly divided by controversies. The issue of gay clergy happens to be the one that is actually splitting the Kirk publicly. Other divisions, less noticeable, are festering away.

The Church of Scotland has always had a fissile tendency. There have been splits and reunions, though never before against a background of strong secularism. Across Scotland, there is little general sympathy for the Kirk's plight; more a casual indifference. Just when the national church needs to be resolute, it is withering away.

In 1843 one of the great events in Scottish history took place. More than 100 ministers marched out of the General Assembly of the Church of Scotland in Edinburgh and decided to form a new church. Soon many other ministers and about 40% of the Kirk's overall membership joined them. At first these folk, many thousands of them, worshipped in fields and barns and big tents. But they showed a remarkable capacity for fundraising and building. All over Scotland, fine new churches – and manses – were built. If something similar were to happen in the next few years, and it could, then the depressed Scottish economy might receive a very considerable boost.

The congregation of St George's Tron did not have a particularly high income. But some evangelical congregations that might be expected to split fairly soon from the mother church are very wealthy indeed, with many generous members.

Twelve years ago I was commissioned by the then moderator of the Church of Scotland, Dr Andrew McClellan, to write a candid book about the condition, situation and prospects of the national church. I concluded that a schism was a distinct possibility but not a probability. My ideas were predicated on the notion that the Kirk should remain our national church. Now I'm certain that a schism is imminent. The best way to prevent it would be if the Kirk, graciously, realistically and carefully, dissolved itself. In its place would be a loose federation of congregations of like-minded people.

Even now, many individual congregations are thriving. They play a vital role in their communities and maintain a relevant, active Christianity in a very secular environment. Crucially, they succeed as individual congregations, rather than small constituent parts of a failing national institution that is beset with irrelevant legalism and bureaucracy.

And that's the irony: at local level, in many areas of our towns and cities and even in parts of our deepest countryside, Presbyterian Christianity is alive and very well. The belief and the commitment are there: it's the structure that's failing.