We shall not trace here the history of the Old Academy, or speak of the innovations on the system of Plato, silently introduced by the austere Polemo. When Zeno, however, who was his pupil, advocated the same rigid tenets in a more open and dogmatic form,[149] the Academy at length took the alarm, and a reaction ensued. Arcesilas, who had succeeded Polemo and Crates, determined on reverting to the principles of the elder schools;[150] but mistaking the profession of ignorance, which Socrates had used against the Sophists on physical questions, for an actual scepticism on points connected with morals, he fell into the opposite extreme, and declared, first, that nothing could be known, and therefore, secondly, nothing should be maintained.[151] Whatever were his private sentiments (for some authors affirm his esoteric doctrines to have been dogmatic[152]), he brought forward these sceptical tenets in so unguarded a form, that it required all his argumentative powers, which were confessedly great, to maintain them against the obvious objections which were pressed upon him from all quarters. On his death, therefore, as might have been anticipated, his school was deserted for those of Zeno and Epicurus; and during the lives of Lacydes, Evander, and Hegesinus, who successively filled the Academic chair, being no longer recommended by the novelty of its doctrines,[153] or the talents of its masters, it became of little consideration amid the wranglings of more popular philosophies. Carneades,[154] therefore, who succeeded Hegesinus, found it necessary to use more cautious and guarded language; and, by explaining what was paradoxical, by reservations and exceptions, in short, by all the arts which an acute and active genius could suggest, he contrived to establish its authority, without departing, as far as we have the means of judging, from the principle of universal scepticism which Arcesilas had so pertinaciously advocated.[155]