Less information exists as to the arguments by which Carneades sought to assail the current principles of morality. Nevertheless, enough is known to indicate the course taken by his Scepticism in relation thereto. In the second of the celebrated speeches which he delivered at Rome in the year 156 B.C., [1496] he denied that there is such a thing as natural right: all laws are only positive civil institutions devised by men for the sake of safety and advantage, and for the protection of the weak; and hence he is regarded as foolish who prefers justice to interest, which after all is the only unconditional end. In support of these statements he appealed to the fact that laws change with circumstances, and are different in different countries. He pointed to the example of great nations, such as the Romans, all of whom attained to greatness by unrighteous means. He impressed into his service the many casuistical questions raised by the Stoics, expressing the opinion that in all these cases it is better to commit the injury which brings advantage—for instance, to murder another to save one’s own life—than to postpone advantage to right, and hence inferred that intelligence is a state of irreconcileable opposition to justice. [1497] This free criticism of dogmatic views could not fail to bring Carneades to the same result as his predecessors. Knowledge is absolutely impossible. A man of sense will look at everything from all sides and invariably withhold judgment, thus guarding himself against error. [1498] And to this conviction he clings so persistently that he altogether refuses to listen to the objection that the wise man must be at least convinced of the impossibility of any firm conviction. [1499] The earlier Sceptics, far from attributing on this ground an equal value to all notions, had not dispensed with reasons for actions and [(2) Positive side of the teaching of Carneades.] [(a) Theory of probabilities.]