Generally regarded as the father of modern philosophy, René Descartes set out on a daring intellectual adventure to try to doubt everything - including his own physical existence. After discovering the impossibility of doubting that he doubted, Descartes came up with the crucial concept of "cogito ergo sum", which became the foundation upon which he created a complete scientific system for dealing with reality, and which has been at the centre of philosophical debate ever since. Descartes was also one of the most important mathematicians in history. And he made major advances in such diverse sciences as physics, physiology, optics and astronomy.
IDEAS host Paul Kennedy looks at the life and legacy of the "first modern man".