Since 1666, [Rene] Descartes' bones have been fought over, stolen, and sold--by adherents to both religious and scientific doctrine. But why? The answer lies in Descartes' legendary expression, 'I think, therefore I am,' which prompted the notion that knowledge can be found in facts, not church teachings. With that seemingly innocuous phrase, Descartes presented skepticism to the world--and profoundly changed the course of humankind.