When Thomas Young was alive the world contained about a billion people. Few of them were literate and fewer still had the chance to experiment on the nature of light or to examine the Rosetta stone. Today the planet teems with 6.7 billion minds. Never have so many been taught to read and write and think, and then been free to choose what they would do with their lives. The electronic age has broken the shackles of knowledge. Never has it been easier to find something out, or to get someone to explain it to you.

Yet as human learning has flowered, the man or woman who does great things in many fields has become a rare species. Young was hardly Aristotle, but his capacity to do important work in such a range of fields startled his contemporaries and today seems quite bewildering. The dead cast a large shadow but, even allowing for that, the 21st century has no one to match Michelangelo, who was a poet as well as a sculptor, an architect and a painter. It has no Alexander von Humboldt, who towered over early-19th-century geography and science. And no Leibniz, who invented calculus at the same time as Newton and also wrote on technology, philosophy, biology, politics and just about everything else.

Although you may be able to think of a few living polymaths who rival the breadth of Young’s knowledge, not one of them beg ins to rival the breadth of his achievements. Over the past 200 years the nature of intellectual endeavour has changed profoundly. The polymaths of old were one-brain universities. These days you count as a polymath if you excel at one thing and go on to write a decent book about another.