Carneades, a Greek philosopher of the Skeptic school, considered as the founder of the third or new academy, born at Cyrene about 213 B. C, died in 129. Of the incidents of his life very little is known, but of his brilliant qualities as a philosopher and rhetorician there is abundant testimony in the works of classic authors. In Athens he became a student of the Stoic and Skeptic doctrines, especially those of Chrysippus, of whom he afterward became the most formidable opponent, His eloquence was considered so irresistible, his logic so forcible, that more than a century later Cicero said, "Him I would not care to challenge in debate, but would rather propitiate him, and implore his silence.1' It is related of him that having been sent to Rome as one of three commissioners of the Athenian commonwealth, he one day made a speech in favor of justice, and the next day one in opposition. His arguments on either side were so convincing, and seemingly unanswerable, that Cato, fearing lest the public mind should be corrupted by such an exhibition of plausible arguments for immorality and injustice as well as for morality and justice, insisted upon a speedy settlement of the diplomatic business for which Carneades had come to Rome, and his prompt dismissal from the city.

He was not an author, but transmitted his doctrines to his disciples by word of mouth, like Socrates. So far as the philosophy of Carneades is known, its substance may be condensed thus: Every perception is a certain change or movement in a sensible being, bringing to consciousness first itself, and secondly some object without. In respect to the object, the perception is either true or false; in respect to the one who perceives, either probable or improbable. There exists no test to decide on the truth or untruth of a perception, that is to say, on the relation which the perception bears to the object by which it is caused. There is no objective certainty, or guarantee that real existing things are essentially reproduced by the human perception; but whatever the relation of human perception to reality, to man himself the mere probability, the test of which lies within the limits of his mind, is sufficient for all practical purposes. Thus much may be designated as the affirmative portion of the philosophy of Carneades; the practical portion was his criticism of the then existing philosophical system, a criticism based merely upon the supposition that the affirmations and negations of human language comprise all existing possibilities, so that if both should be refuted a non est would be proven.

Carneades pretends to prove the non-existence of God by the following reasoning: God is either a rational and sensitive being, or he is not. If he is, then he would be subject to sensations agreeable and disagreeable, to likes and dislikes; but if so, he would be a changeable being, and, as such, liable to destruction. On the other hand, if God is not a rational and sensitive being, then he could not have been the creator of reason and sensation. Again: God is either finite or infinite. If the latter, then he would be motionless, and therefore inactive; if the former, there would be something that was more than he, because limiting him. By similar arguments he gets rid of all general ideas of morality, human rights, duties, etc. But when he seems to have destroyed everything, he suddenly turns round, concluding that all these arguments prove merely that absolute metaphysical knowledge is as unnecessary as it is impossible; that man ought to be satisfied with probabilities and expediencies, which are amply sufficient to secure his well-being.