It was the Russian novelist Fyodor Dostoyevsky who suggested that if you wanted to assess how civilised a country was, you should look at its prisons.
A couple of generations later Winston Churchill - a reforming Home Secretary when he was only 35 - said something very similar. But that was more than a hundred years ago.
Prisons, and prisoners, are too often left well outside the ebb and flow of our public debate. Take the (generally impressive) White Paper on Scotland's Future.
It concludes with 650 questions and answers. Sadly, just two of these deal with Scotland's prisons. The first notes that Scotland has its own prisons - you don't say - and in an independent Scotland criminals sentenced by Scottish courts will be sent to these prisons. The second answer merely confirms that prison transfers could continue between Scotland and the rest of the UK
Little aspiration there, then. Of course the problem with the White Paper is that it is not setting out a vision for an independent Scotland, but rather answering some pretty basic questions, and it does that well. Even so, a little more indication of how an independent Scotland could become a better place would not come amiss.
If you do judge a country by its prisons and how it treats its prisoners, Scotland is not doing badly, but not particularly well either.
By far the biggest problem is the high reconviction rate. Far too many of our prisoners cannot cope when they leave prison. Far too many of them are reconvicted within a year of being freed.
Dr Andrew McLellan, when presenting his final report as chief inspector of prisons in 2009, forcefully made the excellent point that it is hardly surprising that so many liberated prisoners soon end up back in detention when they do not have a job to go to on release.
Even worse, a considerable number of them do not even have a home to go to.
When he was Moderator of the Kirk's General Assembly in 2000 and 2001, Andrew McLellan visited each of Scotland's 16 prisons.
This surprised many in the Kirk, but it helped to remind us of Dostoyevsky's dictum. What goes on in our prisons should concern us all. Prisoners should not be locked up and forgotten.
Yet the real problem concerns not so much what happens in custody, though that is important enough, but what happens when prisoners are set free.
I accept that this is unlikely to be an area of discussion that will engage many people in the run-up to the referendum vote in September, but I hope that there might be some debate about how our prisons could be improved, and about how our prisoners could be better prepared for their eventual freedom - and helped once they are free.
Interestingly, Scotland's own prison officers' association was the first union to come out and publicly back a Yes vote in the forthcoming referendum.
It would be helpful if the prison officers themselves could try to start a debate about how prison might become both more effective and more humane in an independent Scotland.
Scotland's prison population obviously fluctuates but usually there are between 7000 and 8000 who are in custody, and that includes some who are untried. Most of us, including many politicians, ignore these thousands of people; out of sight, for most, and also out of mind.
I understand that many people, and not just those on the political right, think that the way we treat and support victims of crime is a more pressing issue than how we treat those convicted of crime.
But surely they are equally important. In any event, I don't like living in a country where some seem to regard it as an affront if a few prisoners are granted festive leave at Christmas time, and a few more are given special Christmas lunches.
We've obviously progressed a long way since the time when a prison sentence often meant severe illness, insanity or even death for the wretched inmates (some of them young children). But there's still quite a way to go.