ARCESILAUS, a Greek philosopher, and founder of the New or Middle Academy, was born at Pitane in Aeolia, about 316 b.c. He received careful training in his youth from the mathematician Autolycus, and then proceeded to Athens, where for some time he studied under Theophrastus. He was gained over to the Academy by Crantor, with whom he continued to live on terms of the closest intimacy. After the death of Crantor, Arcesilaus continued to study under Polemo and then under Crates, whom he succeeded as leader of the school. There is a little doubt as to the philosopher’s mode of life. According to some he lived in extravagant, even profligate style, and Diogenes Laertius tells us that he died in his 7 5th year of excessive drinking. But the testimony of others, e.g., Cleanthes, seems to show that he practised extreme moderation; and some of his practical precepts tend to confirm this view. He was much beloved and respected by the Athenians, and is celebrated for his acuteness, eloquence, and learning. His philosophical opinions can only be gathered from scattered notices in Cicero, Sextus, and others. He advocated the Socratic or colloquial method of discussion, although he depreciated dialectic proper, and seems to have carried out thoroughly the sceptical element in the Platonic school. His theory of knowledge was developed in direct antagonism to that of the Stoics. He especially opposed their favourite doctrine, that the criterion of truth was to be found in the irresistible or irresistibly convincing impression, which served as a mean between science and opinion, and was common to the wise man and the foolish. Arcesilaus denied that such a mean was possible, and showed further, that as conviction implied approval or judgment, it could not apply to impressions but only ...