consider the arguments of the Stoics and the sophisms of the Megarians as useless, whilst, at the same time, he was convinced that no real knowledge could be attained by any other means. He might even have inferred from their sterility, that thought leads to truth quite as little as the senses. There is no real difference between the result at which he arrived and that of Pyrrho. [1440] If opponents asserted that by denying knowledge all possibility of action is denied, [1441] Arcesilaus declined to accede to this statement. No firm conviction is, as he maintained, necessary for a decision of the will; for an action to come about a perception influences the will immediately, leaving the question as to its truth entirely out of sight. [1442] In order to act sensibly [(2) Probability.] we need no knowledge; for this purpose probability is quite enough; any one can follow probability, even though he is conscious of the uncertainty of all knowledge. Thus probability is the highest standard for practical life. [1443] We are but scantily informed how Arcesilaus applied this principle to the sphere of morals, but a few of his utterances are on record. [1444] All bear witness to the beautiful spirit of moderation in the moral theory of the Academy, which was otherwise exemplified in his own life. [1445] [B. Carneades.] Comparing with the theory of Arcesilaus that which was propounded by Carneades a century later, the same leading features are found to be underlying; but the points have been more carefully worked out, and the theory placed on a wider footing. Of the immediate followers of Arcesilaus [1446] it can only be stated that they clung to their teacher. It may be presumed that they did little in the way of expansion, since the ancients are silent as to their labours; Carneades [1447] is only mentioned as the continuer of the Academic Scepticism. The importance of Carneades is therefore very great, whence he is in consequence called the founder of the third or New Academy; [1448] and it is justly great, witness the admiration which his talents called forth among cotemporaries and posterity, [1449] and the flourishing condition in which he left his School. [1450] Himself a pupil of Chrysippus, and resembling him in tone of mind, [1451] Carneades expanded not only the negative side of the Sceptical theory in all directions with an acuteness entitling him to the first place among the ancient Sceptics, but he was also the first to investigate the positive side of Scepticism, the doctrine of probability, and to determine the degrees and conditions of probability. By his labours in both ways he brought the philosophy of Scepticism to its greatest scientific perfection. [(1) Negative side of his teaching.]