Descartes is one of the founders of the modern world. His famous method of doubt was one of Europe’s first steps towards the Enlightenment and the scientific revolution. And of all the thinkers of his time who were making similar moves, and similar discoveries, he is the one with true fame, whose works are read by every first-year philosophy student, and whose founding axiom ‘Cogito, ergo sum’ is almost as well known as God’s ‘Let there be light’ – nowadays, indeed, probably better. If anyone merits a biography, Descartes does.

The trouble is that almost nothing is known of his life, and what little is known is subject to almost Cartesian doubt. For nearly a decade he wandered war-torn Europe, no one knows why; in his last twenty peaceful Dutch years he kept his many addresses secret; and his death,