What is the meaning of ‘life’? Well, it’s the alternative to death. Not least in British penal policy.

Back in the 1950s and 1960s when the UK was phasing out capital punishment, politicians came up with what they thought sounded like a tough alternative.

Killers, they said, should get life, not death. Some made being behind bars for all your days sound even worse than the quick snap of the noose.

More than half a century later many Britons - including some right wing politicians north of the border - are still in thrall to this desire to punish.

Scottish Tories have even suggested their own answer to the eternal question: life they reckon should mean life, at least sometimes.

Professor Dirk Van Zyl Smit is not so sure. In fact, he reckons Conservative plans for whole life tariffs would be unlawful under European rights regime Britain is remaining in after Brexit.

The academic is currently looking at how many lifers are behind bars around the world. His findings might shock some: Scotland has twice as many as France in absolute terms. His comparison is broadly fair although, of course, France does not have the automatic life sentences we imposed for all murderers. You only get life in France if you commit a very serious murder, such as a terror attack. And he is not comparing sentences for murder: our lifers can get a minimum sentence even if, after release, they remain on licence till they die.

Like Scotland and England, Germany hands out life sentences for all murders. But it defines murder far more narrowly than we do. The Netherlands has whole life sentences, but only 30 lifers. Scotland has 1000. Russia, where jail conditions admittedly can be very bad, has just 1800.

Some 30 jurisdictions have abolished life sentences as well as capital punishment (only one European state, Belarus, has the death penalty).

Scotland likes to pitch itself as progressive. The SNP has made baby steps towards cutting our prison population, among the highest in western Europe, by ending short-term sentences. Do they have the political confidence to do the same for longer ones?