Ancient skepticism, Epicureanism and Stoicism

Ancient Skepticism - Skeptics questioned certainty in knowledge, including Plato's and Aristotle's philosophies.  Much later, Galileo undermined Aristotle's views of physics which had long been deemed certain, and the Magellan's voyage around South America undermined Aristotle's (and Augustine's) claim that it was impossible to live below the equator.  Through this, "any reflective person" could see there was "no certainty, no undisputed source of knowledge in the world." (40).

Pyrronian (radical) skepticism went much further than questioning authority.  It held that nothing could truly be known and that (there could be no real difference between "yes" and "no").      

Ancient Epicureanism  -  Epicureans believed that pain was to be avoid, and they withdrew from public society into isolated communities for contemplation.  They also believed the origins of the world was only material and no deity was involved in creating or governing the world.  Epicureans were accused by many Enlightenment philosophers, that in saying that the fundamental goal of life was to minimize pain and maximize pleasure, of saying all human life was nothing but a calculation of pain and pleasure, or egoism.  And they associated Thomas Hobbes with Epicureans to denounce his philosophy.  

Stoicism  -  Stoics differed from Epicureans in that their philosophy was derived from the world as a whole rather than from the individual.  They believed the world was harmonious and had a transcendental purpose.  Extremes of emotions, either good or bad, were to be avoided.  Life's events should be taken impassively, whether to his emotions or the emotions of others.  The French revolutionary, the Marquis de Condorcet, saw this as an excuse not to help others with troubles.  But most Enlightenment thinkers admired the Stoic's views of a purposeful, harmonious universe.