Philosophical skepticism is different than skepticism in everyday conversations. Epistemological skepticism can"t prove you aren"t dreaming or plugged in to the matrix. All of a person"s knowledge claims are to be rejected except for the knowledge of one"s current perceptual state. The active disbelief in an external world is just as unbounded as an active belief in the external world. Ancient skeptics - a natural response to adopt towards skepticism is a blissful detachment from the world. Modern skeptics - the natural response is repugnance. Skepticism died down until the 15th and 16th century religious and scientific evolution. Descartes was one of the most influential writers on skepticism. Said he had to forget everything he"s ever learned. Our senses deceive us -- no way of knowing external reality. Can"t tell dreaming life from waking life. Cogito ergo sum i think therefore i am. Empiricist knowledge comes from our senses, which deceive us. Descartes is not justified in cogito ergo sum.