Rene Descartes was a central figure in the scientific revolution of the seventeenth century. In his Discourse on Method he outlined the contrast between mathematics and experimental sciences, and the extent to which each one can achieve certainty. Drawing on his own work in geometry, optics, astronomy and physiology, Descartes developed the hypothetical method that characterizes modern science, and this soon came to replace the traditional techniques derived from Aristotle. Many of Descartes' most radical ideas - such as the disparity between our perceptions and the realities that cause them - have been highly influential in the development of modern philosophy.
Epictetus (c. 55-135 AD) was a teacher and Greco-Roman philosopher. Originally a slave from Hierapolis in Anatolia (modern Turkey), he was owned for a time by a prominent freedman at the court of the emperor Nero. After gaining his freedom he moved to Nicopolis on the Adriatic coast of Greece and opened a school of philosophy there. His informal lectures (the Discourses) were transcribed and published by his student Arrian, who also composed a digest of Epictetus' teaching known as the Manual (or Enchiridion).