NICOLA Sturgeon urged a care for equality on Donald Trump (fat chance) when she finally got round to sending him her congratulations a couple of days ago.

Equality seems to be the word of the week, what with a major report from Professor Glen Bramley of Heriot-Watt University and with BBC Scotland devoting a series to the subject.

It is a subject that also tends to call forth shrill comments from Scottish pundits, not least in this newspaper, but Professor Bramley’s assessment was sober. Of course Scotland’s society is an unequal one, like all other societies that encourage freedom and diversity – with the inevitable result that about half the people will do better than the average, and about half worse, while a few will do much better, a few much worse. “But Scotland’s income inequality is not as extreme as portrayed in some political debate.… By international standards, income inequality is mid-range.” If that sounds outrageous, please read the report. You will soon be put right.

Since I started writing for The National, I have devoted the odd column to inequality myself, meeting reactions from readers usually sent back more in sorrow than in anger. How can anybody live in Scotland and doubt the value of equality? Isn’t it one of the defining features of Scottish society, at least in our aspirations? Above all, isn’t it a feature that sets us apart from the society to the south, which not only tolerates inequality but even promotes and praises it as a sort of virility symbol?

The short answer is that I do believe in equality, at least in the legal and political spheres. We are all citizens of one country, the weight of our votes should be exactly the same and we should have equal access to the law to secure our rights or to redress the wrongs done to us. I think, to put it another way, that we should set off from a single starting line. But I’m not worried if we don’t arrive together at the finishing post, mainly because I don’t believe this is possible anyway. To wish for it, or to act as though it might be possible, is just a waste of physical effort and mental energy.

What makes me suspicious of Scottish usage of the concept of equality is the way it is bandied about with little concern for what it is going to mean in practice. The First Minister herself has said the basic reason she favours the nation’s independence is as a means to the end of greater equality among its people. Well, I think I will be able to recognise the nation’s independence when I see it. The equality will be much harder to identify, because neither Nicola nor anybody else has told me what it is going to look like.

Let me give examples of details I would like to see filled in – first, examples going through time. Average income in Scotland is about £25,000 a year. At the bottom of the pay scale is a trail of people who have less than £20,000 a year, the poorest of these either on benefits or getting their income topped up by benefits (469,000 people). And towards the top of the scale are the rich, about 100,000 people on the higher rate of tax earning more than £43,000 a year. On top of that come 14,000 people on the additional rate earning more than £150,000 a year, sometimes called the super-rich.

It would be foolish to think that, as the solution to inequality, we only need to squeeze these super-rich. If in a given year we didn’t merely tax but confiscated their entire incomes, it would just about cover Scotland’s budget for social protection in that year. Would we in any way be morally justified in doing this? They are not every one of them hedge fund managers or property speculators. Many deserve what they get. Top surgeons can earn more than £150,000 a year. Isn’t that the right sort of reward for their rare expertise in cutting out brain tumours?

We learned this week that the average pay for members of the first team at Celtic FC is more than £700,000 a year. Should the Bhoys be shoved back to £25,000 a year? If it did happen, I don’t think professional football at Parkhead or anywhere else in Scotland would go on much longer.

All this is by way of saying that if we want any big reduction in inequality then we have to achieve it among the middle range of earners where the vast bulk of the nation’s incomes are earned. In other words, the gap between people on £20,000 a year and £30,000 a year must be cut so that they converge towards £25,000 a year.

But is there any good reason, apart from the principle of equality, why we should want to do this? After all, a lot of the differential is simply the result of age. People start off at the bottom of the scale for their job, and as they gain experience, get promoted or move for a better opportunity they earn more. Is it really a good idea that workers at the age of 50 should take home about the same pay as youngsters who have just started at the age of 20? Yet that is what equality would mean in practice. If we cannot face this, we should stop going on about equality.

Let’s look at the distribution of incomes across any given point in time. I would guess that a big part of the intellectual problem for the Scottish Government is that it believes there is some state of equilibrium where the distribution of incomes would be as equal and just as anybody could ever make it. The concept is nonsense.

The economy changes constantly: change is its normal condition, not some stationary state. Just now, for example, companies in the north-east of Scotland servicing the oil industry are having a hard time because of the crash in the price of crude, and a good many have already gone bust. At the same time, the computer games industry in Dundee and Edinburgh is booming, and has become one sector in which Scotland leads the world.

The question is this: with similar qualifications and abilities, should the Scots working in North Sea services earn and continue to earn about the same as the Scots who produce computer games? Let’s say for the sake of the argument that the figure is £25,000 a year. It’s obvious the service companies in Aberdeenshire are already finding it hard to pay that kind of money, which is why they are laying off workers so fast. Yet if we tried to tell the computer whizz-kids that £25,000 is all they can earn, and right to the end of their careers as well, then they would just laugh before getting the next flight out to San Francisco or Hong Kong.

These are, as I see them, some of the practical problems of equality as elevated to public policy. The project appears hopelessly impractical as soon as you start to dig into it. That is why I tend to think our talk of equality, in Scotland and in its government, is a sham. We prattle on about it because we have not even begun to think seriously about what it means. It may make us feel good, but it is no way to run a country.