With the celebrated words 'I think therefore I am', Descartes' compelling argument swept aside ancient and medieval traditions. He deduced that human beings consist of minds and bodies; that these are totally distinct 'substances'; that God exists and that He ensures we can trust the evidence of our senses.
Ushering in the 'scientific revolution' of Galileo and Newton, Descartes' ideas have also set the agenda for debate ever since.
By calling everything into doubt, Descartes laid the foundations of modern philosophy.
