Rene Descartes gave Western philosophy its most famous sentence — "I think, therefore I am" — and laid the foundations for modern rationalism. But after his death in Stockholm, his remains became the subject of one of intellectual history's strangest sagas: his skull was stolen, passed between collectors for centuries, and became a relic as contested as any saint's bones.

This episode traces Descartes from his meditations in a heated Dutch stove-room through the revolutionary Discourse on Method and his ill-fated move to Sweden, then follows the bizarre posthumous journey of his stolen skull across Europe.

• Descartes's radical method of doubt and the "cogito" that rebuilt philosophy from scratch
• His years of self-imposed exile in the Dutch Republic and the works he published there
• The invitation to Queen Christina' ...