This is the first book-length study of Philo of Larissa. Philo (159-84 BC) was the leader of the Platonic Academy in its final period as an Athenian institution, and also the principal philosophical teacher of Cicero. Dr Brittain charts Philo''s gradual rejection of the radical scepticism of Carneades (concluding with his notorious ''Roman Books'' of 89 BC), and offers philosophical justifications for his initial position of modified scepticism and final advocacy of a fallibilist empiricism. Philo''s controversial epistemological views are constructed through their historical context in the late Hellenistic Academy, his wider thought on the history of philosophy, ethics and rhetoric, and his controversies with his pupils Antiochus and Aenesidemus. The appendix contains full testimonia and ''fragments'' of Philo.