(Ἀρκεσίλαος) or ARCESILAS, the founder of the new Academy, flourished towards the close of the third century before Christ. (Comp. Strab.i.p.15.) He wasthe son of Seuthesor Scythes (D. L. 4.18), and born at Pitane in Aeolis. His early education was entrusted to Autolycus, a mathematician, with whom he migrated to Sardis. Afterwards, at the wish of his elder brother and guardian, Moireas, he came to Athens to study rhetoric; but becoming the disciple first of Theophrastus and afterwards of Crantor, he found his inclination led to philosophical pursuits. Not content, however, with any single school, he left his early masters and studied under sceptical and dialectic philosophers; and the line of Ariston upon him, Πρόσθε Πλάτων, ὄπιθεν Πύρ̀ῥων, μέσσος Διόδωρος, described the course of his early education, as well as the discordant character of some of his later views. He was not without reputation as a poet, and Diogenes Laertius (4.30) has preserved two epigrams of his, one of which is addressed to Attalus, king of Pergamus, and records his admiration of Homer and Pindar, of whose works he was an enthusiastic reader. Several of his puns and witticisms have been preserved in his life by the same writer, which give the idea of an accomplished man of the world rather than a grave philosopher. Many traits of character are also recorded of him, some of them of a pleasing nature. The greatness of his personal character is shewn by the imitation of his peculiarities, into which his admirers are said insensibly to have fallen. His oratory is described as of an attractive and persuasive kind, the effect of it being enhanced by the frankness of his demeanour. Although his means were not large, his resources being chiefly derived from king Eumenes, many tales were told of his unassuming generosity. But it must be admitted, that there was another side to the picture, and his enemies accused him of the grossest profligacy--a charge which he only answered by citing the example of Aristippus--and it must be confessed, that the accusation is slightly confirmed by the circumstance that he died in the 76th year of his age from a fit of excessive drunkenness; on which event an epigram has been preserved by Diogenes.

It was on the death of Crantor that Arcesilaus succeeded to the chair of the Academy, in the history of which he makes so important an era. As, however, he committed nothing to writing, his opinions were imperfectly known to his contemporaries, and can now only be gathered from the confused statements of his opponents. There seems to have been a gradual decline of philosophy since the time of Plato and Aristotle : the same subjects had been again and again discussed, until no room was left for original thought--a deficiency which was but poorly compensated by the extravagant paradox or overdrawn subtlety of the later schools. Whether we attribute the scepticism of the Academy to a reaction from the dogmatism of the Stoics, or whether it was the natural result of extending to intellectual truth the distrust with which Plato viewed the information of sense, it would seem that in the time of Arcesilaus the whole of philosophy was absorbed in the single question of the grounds of human knowledge. What were the peculiar views of Arcesilaus on this question, it is not easy to collect. On the one hand, he is said to have restored the doctrines of Plato in an uncorrupted form; while, on the other hand, according to Cicero (Cic. Ac. 1.12), he summed up his opinions in the formula, "that he knew nothing, not even his own ignorance." There are two ways of reconciling the difficulty : either we may suppose him to have thrown out such ἀπορίαι as an exercise for the ingenuity of his pupils, as Sextus Empiricus (Pyrrh. Hypotyp. 1.234), who disclaims him as a Sceptic, would have us believe; or he may have really doubted the esoteric meaning of Plato, and have supposed himself to have been stripping his works of the figments of the Dogmatists, while he was in fact taking from them all certain principles whatever. (Cic. de Orat. 3.18.) A curious result of the confusion which pervaded the New Academy was the return to some of the doctrines of the elder Ionic school, which they attempted to harmonize with Plato and their own views. (Euseb. Pr. Ev. 14.5, 6.) Arcesilaus is also said to have restored the Socratic method of teaching in dialogues; although it is probable that he did not confine himself strictly to the erotetic method, perhaps the supposed identity of his doctrines with those of Plato may have originated in the outward form in which they were conveyed.

The Stoics were the chief opponents of Arcesilaus ; he attacked their doctrine of a convincing conception (καταληπτικὴ φαντασία) as understood to be a mean between science and opinion--a mean which he asserted could not exist, and was merely the interpolation of a name. (Cic. Ac. 2.24.) It involved in fact a contradiction in terms, as the very idea of φαντασία implied the possibility of false as well as true conceptions of the same object.

It is a question of some importance, in what the scepticism of the New Academy was distinguished from that of the followers of Pyrrhon. Admitting the formula of Arcesilaus, "that he knew nothing, not even his own ignorance," to be an exposition of his real sentiments, it was impossible in one sense that scepticism could proceed further : but the New Academy does not seem to have doubted the existence of truth in itself, only our capacities for obtaining it. It differed also from the principles of the pure sceptic in the practical tendency of its doctrines : while the object of the one was the attainment of perfect equanimity (ἐποχή), the other seems rather to have retired from the barren field of speculation to practical life, and to have acknowledged some vestiges of a moral law within, at best but a probable guide, the possession of which, however, formed the real distinction between the sage and the fool. Slight as the difference may appear between the speculative statements of the two schools, a comparison of the lives of their founders and their respective successors leads us to the conclusion, that a practical moderation was the characteristic of the New Academy, to which the Sceptics were wholly strangers. (Sex. Empiricus, ad v. Math. 2.158, Pyrrh. Hypotyp. 1.3, 226.)