The first was Pyrrhonism, was founded by Pyrrho of Elis (c. 360–270 BCE). The second was Academic Skepticism, so-called because its two leading defenders, Arcesilaus (c. 315–240 BCE) who initiated the philosophy, and Carneades (c. 217–128 BCE), the philosophy's most famous proponent, were heads of Plato's Academy. hope this helps
