René Descartes

Descartes (1596-1650) is known as the father of modern philosophy, in that his philosophy spells an end to medieval scholasticism. His interest for epistemology lies in his explicit attempt to discover what he could know, based on a preliminary examination of the competence of his faculties. The end-result was the establishment of his own existence, the fact that he is a mind, the existence of God, and the existence of the external world.

In the process of evaluating his faculties, Descartes considered various ways in which they might go wrong. The senses are well known for revealing misleading appearances. Moreover, there may be no senses at all, since it is impossible to distinguish with certainty (based on how they appear) dreaming from waking. Thus a central challenge of epistemology is to prove that an external world exists.

An even deeper challenge results from something that Descartes took to be a possibility: that there exists a being powerful enough to deceive him about those matters which are most obvious. It might be held that if this is a real possibility, then we are almost completely ignorant. Much work in epistemology has been devoted to understanding the significance of the "demon hypothesis" and, when it is considered a real threat to knowledge, coming to grips with it.

For a comprehensive account of Descartes's Meditations, see my lecture notes on Descartes for Philosophy 22.

For a more basic account of the Meditations, see my notes for Philosophy 1.