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(ärsĕs'ĭlā`əs), c.316–c.241 B.C., Greek philosopher of Pitane in Aeolis. He was the principal figure of the Middle Academy. Despite his position in the AcademyAcademy,
school founded by Plato near Athens c.387 B.C. It took its name from the garden (named for the hero Academus) in which it was located. Plato's followers met there for nine centuries until, along with other pagan schools, it was closed by Emperor Justinian in A.D. 529.
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, his teachings diverged from Platonic doctrine. By emphasizing the doubt expressed by Socrates as to the possibility of gaining knowledge, he took a position comparable to that of the Skeptics (see skepticismskepticism
[Gr.,=to reflect], philosophic position holding that the possibility of knowledge is limited either because of the limitations of the mind or because of the inaccessibility of its object. It is more loosely used to denote any questioning attitude.
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). He argued that knowledge and opinion could not be distinguished from each other, so that what anyone claims to know may be more or less probable but not certain. In denying the possibility of certainty he was a major opponent of the Stoics (see StoicismStoicism
, school of philosophy founded by Zeno of Citium (in Cyprus) c.300 B.C. The first Stoics were so called because they met in the Stoa Poecile [Gr.,=painted porch], at Athens, a colonnade near the Agora, to hear their master Zeno lecture.
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). Arcesilaus indirectly influenced CarneadesCarneades
, 213–129 B.C., Greek philosopher, b. Cyrene. He studied at Athens under Diogenes the Stoic, but reacted against Stoicism and joined the Academy, where he taught a skepticism similar to that of Arcesilaus.
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 and his school.


See A. A. Long, The Hellenistic Philosophers (2 vol. 1987).

References in classic literature ?
Peneleos, Leitus, Arcesilaus, Prothoenor, and Clonius were captains of the Boeotians.
Ancient scepticism' is a term that standardly encompasses two philosophical traditions stretching from the third century BCE to approximately the second century CE: Pyrrhonism, named after its eponymous founder Pyrrho of Elis (360-270 BCE), and Academic scepticism, a sceptical movement which arose in the Platonic Academy around 268 BCE, when Arcesilaus of Pitane (316/5-241/0) became its head.
Thorsrud argues for a dialectical interpretation of Arcesilaus, insisting that Arcesilaus' central theses, namely that nothing can be known and that we should suspend judgement, are modelled on Socratic dialectic and do not represent his own position.
82) The ancient Skeptics, Arcesilaus and Carneades in particular, however, showed clearly that no subjective impression purporting to reveal anything about the world beyond consciousness can bear its own warrant.
48) The thesis is attributed to Carneades by Sextus Empiricus (Against the Professors 7, 159-65), and can be traced back to Arcesilaus (Cicero, Academica 2.
Sextus reports Arcesilaus as having prepared for the Stoic claim that katalipsis, which is the criterion of truth, is between knowledge and opinion; on Meinwald's view each side is proceeding in a philosophically legitimate way.
The lecture format also accounts for the peculiarities of grouping: putting Pyrrho and Arcesilaus together encourages assimilation of two distinct sceptical traditions, while the separation of Philo of Larissa from Antiochus of Ascalon makes it particularly hard to tell an intelligible story about the last stages of the Hellenistic Academy.