BORDERS are both administratively necessary and symbolically significant. It is impossible to create a system of government with even a modicum of public services or have representative democracy without borders simply because we need “geographical units of government”.

Geographical units of government, of course, depersonalises the matter. Symbolically, these units attain a status dividing “us” and “them”. The key questions are, firstly, where to draw the border or boundary, secondly, its purpose and, thirdly, how porous it should be.

Many of currently all too typically heated contributions focus exclusively on the symbolism and pay little heed to the public policy dimension. Sadly, that has been an all too familiar feature of our politics.

READ MORE: UK Government 'planning to withhold power from Scotland after Brexit transition'

We have been witnessing a significant change in Conservative unionism under Boris Johnson. David Cameron’s “respect agenda” was largely rhetorical but was more pluralistic compared with current Tory leader. Indeed, Mr Johnson’s unionism goes well beyond Margaret Thatcher’s.

Mrs Thatcher never understood the multi-national nature of the UK and, as her memoirs made clear, she was irritated by a Scottish Office that pursued different agendas and policies from her own. But she never denied that Scotland was a distinct nation or that there was no border.

What we are seeing is the rise of a kind of unitary state unionism that has never previously existed and sits very uneasily with devolution. In research I conducted in the early ways of devolution, I argued that we may have created devolved institutions but had still to develop a devolved mindset or culture in the UK.

That was slowly developing but appears to have come to a juddering halt with this Prime Minister. His rhetoric on borders would suggest that devolved government should not exist. This does not mean he will seek to abolish the Scottish Parliament but seeks to frustrate it.

The Anglo-Scottish border is remarkably clear – there are no border disputes as exist in many parts of the world. It is real, defined legally and administratively. It is absurd to pretend otherwise but it is not absurd to question its purpose or how permeable it should be.

In public policy terms – less exciting but more important in terms of services people receive – borders are necessary. Boundaries – whether between components of a federation, a (partially) devolved polity or local government – allow for diversity in policy prescriptions reflecting different needs. From a purely public policy perspective, the most appropriate units and thereby boundaries, will differ depending on the function or service. The most boundaries for the provision of important aspects of economic planning are arguably far greater than for parks and leisure. It may be necessary to combine for certain functions.

As far as trade is concerned, local authorities are far too small, so too is Scotland and indeed so too is the UK. Hence we need permeable borders.

That is all very abstract but these have been questions that have had to be tackled over the 20th century with every major overhaul of local government – about every 20 to 30 years or so – and also considering whether a matter should be administered at a Scotland, Britain or UK level. It has also been key in debates on European integration – the issue of subsidiarity.

Translating this into examples. One interesting debate that I wrote about many years ago concerned the state’s increasing intervention in animal and public health.

When the UK decided there needed to be a ministry responsible for agriculture including animal health, the question arose as to whether the border should be ignored or whether there should be a distinct Ministry for Scotland with responsible for animal health in Scotland.

READ MORE: Opinion: Mark Smith: Scottish independence is not inevitable, but we all need to change the way we look at it

Some Whitehall officials feared a Scottish ministry might be more lax and that porous nature of the border would mean that diseased animals would easily stray over the border and infect “English” animals – foot and mouth for example. But Scottish officials insisted and have subsequently been proved correct in arguing that Scotland would have at least as stringent animal health regulations, administration.

The permeable or porous nature of borders is important but requires flexibility. What we are seeing across the world – both within and between states – is that borders that are normally very porous have been temporarily firm or less permeable for sensible public health reasons.

This comes at a cost of course. Creating a hard border inevitably has an adverse effect on trade and the economy.

A legitimate case can be made to harden the Anglo-Scottish border temporarily for public health reasons and, equally, an economic case can be made for keeping that border open. This should not be a question based on anything other public policy considerations.

There are two ways of looking at this – weighing up the balance between economic and health risks, which is not easy, or making a decision based on symbolism and sentiment.

It is clear that the First Minister is considering this in public policy terms, as indeed she should.

James Mitchell is Professor of public policy at Edinburgh University.