2. THE NEW ACADEMY.—Scepticism, in its conflict with the Stoics, as it appeared in the Platonic school established by _Arcesilaus_ (316-241), has a far greater significance than belongs to the performances of the Pyrrhonists. In this school Scepticism sought its support by its great respect for the writings and its transmission of the oral teachings of Plato. Arcesilaus could neither have assumed nor maintained the chair of instruction in the Academy, had he not carefully cherished and imparted to his disciples the impression that his own view, respecting the withholding of a decisive judgment, coincided essentially with that of Socrates and of Plato, and if he had not also taught that he only restored the genuine and original significance of Platonism, when he set aside the dogmatic method of teaching. An immediate incitement to the efforts of Arcesilaus is found in his opposition to the rigid dogmatic system which had lately arisen in the Porch, and which claimed to be in every respect an improvement upon Platonism. Hence, as Cicero remarks, Arcesilaus directed all his sceptical and polemic attacks against Zeno, the founder of Stoicism. He granted with his opponent that no representation should form a part of undoubted knowledge, if it could possibly have arisen through any other object than that from which it actually sprung, but he would not admit that there might be a notion which expressed so truly and accurately its own object, that it could not have arisen from any other. Accordingly, Arcesilaus denied the existence of a criterion which could certify to us the truth of our knowledge. If there be any truth in our affirmations, said he, we cannot be certain of it. In this sense he taught that one can know nothing, not even that he does know nothing. But in moral matters, in choosing the good and rejecting the evil, he taught that we should follow that which is probable.
Of the subsequent leaders in the new Academy, _Carneades_ (214-129) alone need here be mentioned, whose whole philosophy, however, consists almost exclusively in a polemic against Stoicism and in the attempt to set up a criterion of truth. His positive performance is the attempt to bring out a philosophical theory of probabilities. The later Academicians fell back to an eclectic dogmaticism.