Descartes' Method of Doubt Biography Rene Descartes (1596-1650) Born in La Haye, a small town in Touraine, France. Educated at the Jesuit college Wrote Meditations Descartes is extremely important to Western intellectual history Contributions in physiology, psychology, optics, and especially mathematics Introduced analytic geometry Influential in modern scientific approach (can't just say it's true, show it's true) The Cartesian Method Descartes is very concerned with skeptical questions Though he was not actually a skeptic, he used skepticism as a method of achieving certainty. "I will doubt everything that can possibly be doubted, and if anything is left, then it will be absolutely certain. Then I will consider what it is about this certainty (if there is one) that places it beyond doubt, and that will provide me with a criterion of truth and knowledge, a yardstick against which I can measure all other purported truths to see if they, too, are beyond doubt." Doubt In order to doubt everything he could, Descartes used two conjectures Dream conjecture Evil demon conjecture Descartes was just as aware of how bizarre these ideas are as we are... that was his point, to doubt anything that had even the tiniest possibility to be false Cogito Ergo Sum Descartes realized that he could, in fact, doubt "absolutely everything, save one indubitable truth: I think, therefore I am" The self that doubts it's own existence must exist to be able to doubt Moreover, a self that doubts must not only exist, but must exist rationally (being a thing that thinks) The "Absolute" Once Descartes established that he doubted everything except that which cannot be doubted (his doubting) -he wanted a yardstick that he could measure all other things by to see if they are true beyond all doubt. This yardstick is clarity and distinctness Those things that are clear and distinct are true.

What is clear and distinct Mathematical concepts There is no perfect circle in nature, but we know what a perfect circle is God Descartes, armed with his clear and distinct test discovers that he has certain knowledge that God exists 3 Proofs 1) The idea of God must come from a reality that is at least as perfect as the idea 2) -I exist as a thing that has an idea of God -Everything that exists has a cause that brought it into existence and that sustains it in existence -The only thing adequate to cause and sustain me, a thing that has an idea of God, is God -Therefore God exists A thing needs a cause to be sustained God is invoked by Descartes as the cause of him 3) -My conception of God is the conception of a being that posses all perfections -Existence is perfection -Therefore I cannon conceive of God as not existing -Therefore God exists Ontological Everything Else Once Descartes was able to prove God exists he felt he could believe what he first doubted If God is supreme good, he / she is incapable of deceit If God is incapable of deceit, the reality of the world can be accepted because God would not have us perceive a world that did not, in fact, exist.