Arcesilaus, Carneades and the Skeptical Academy

Remarkably, Plato's own Academy became a center of skepticism. Around 268 BCE Arcesilaus became its head and revived Socrates' method of arguing against every position while claiming no knowledge himself. His main target was the Stoics, who claimed that some sense impressions are so clear they guarantee truth. Arcesilaus argued that for any true impression there could be a false one indistinguishable from it, so certainty is impossible.

A century later Carneades (214–129 BCE) refined the attack and proposed that we can act on what is 'persuasive' or probable, even without certainty, an early theory of probable belief. In 155 BCE, on an embassy to Rome, he argued for justice one day and against it the next, alarming conservative Romans. The Skeptical Academy shaped Cicero, who studied with its last head, Philo of Larissa, and it showed how a school can transform its founder's legacy.