This article examines the basis of Cartesian skepticism as contained in René Descartes' Meditation 1. It traces the complex argumentation of Meditation 1 and explores the differences between Cartesian skeptical arguments and the skeptical arguments discussed in the ancient world. It suggests that the radical nature of the doubts raised by Descartes is rooted in the radical error that Cartesian science posits in our everyday experience of the world and the hypothetical and morally certain nature of the scientific edifice that is proposed to replace the commonsense view of the world enshrined in Aristotelian science.