Why did Scotland, far poorer than England, produce thinkers like Hume and Adam Smith?

Not through wealth but, the record suggests, through what it had instead: schools, universities and a habit of argument. By the eighteenth century it had a network of parish schools in the Lowlands and five universities. At the union of 1707, England had about five times Scotland's population and about 36 times its wealth, but only two universities.

The union itself reshaped Scottish life. It ended the Scottish Parliament, and the politicians and aristocrats moved to London. The Church of Scotland's leadership, the universities and the medical establishment stayed, and lawyers, ministers, professors and doctors formed a new middle-class elite that facilitated the Scottish Enlightenment.

Their culture was bookish and sociable. Intense discussions took place daily in Edinburgh clubs such as the Select Society, formed by the artist Allan Ramsay with the philosophers David Hume and Adam Smith. The aims were practical: improvement, virtue and benefit for individuals and society.

The results were bold. Hume argued that our belief that one event causes another cannot be justified empirically and comes from custom and mental habit. Smith argued in 1759 that morality depends on sympathy between the person acting and a spectator, and later wrote The Wealth of Nations, described as the starting point of modern economics. Both men met suspicion: Hume's alleged atheism derailed his hopes of a university job.