Rene Descartes: The first modern philosopher

In addition to transforming mathematics, the Frenchman broke with more than a thousand years of thinking to bring about a new era of rationalism – in the process giving us the famous phrase ‘I think, therefore I am’

Descartes used methods learned from maths in his philosophical works (Getty)

Rene Descartes (1596–1650) is the author of perhaps the most famous philosophical quote of all, cogito ergo sum, usually rendered as I think, therefore I am. There is however more to this quote, and more to Descartes’ philosophy, than meets the eye.

Descartes was reasonably young when burning astronomers seemed to the Church the right thing to do. Orthodox thinking at the time regarded the Earth as the centre of the created order, with the heavenly bodies – all perfect spheres – tracing arcs around the Earth in divinely ordained, circular orbits. Not only did Galileo see through his telescope moons orbiting something else, namely Jupiter, but he observed too that at least some of the planets were not themselves perfect spheres: they were bumpy, irregular, maybe squashed. Some looked a bit cracked and pockmarked – not at all the kind of shoddy work one expects from the creator. Despite the Church’s warnings, Galileo pursued all of this in writing. He attracted the attention of the Inquisition, which forced his public recantation.