CARNEADES THE SKEPTIC

Carneades (ca. 213-ca. 128 B.C.) was a Greek philosopher of the third school of academic skepticism. His combination of skepticism and empiricism can now be seen to have remarkable affinities with a good deal of post-Renaissance Western philosophy. He was the first of the philosophers to pronounce the failure of metaphysicians who endeavored to discover rational meanings in religious beliefs. By the time of 159 BC he had started to refute all previous dogmatic doctrines, especially Stoicism, and even the Epicureans whom previous skeptics had spared. As head of the Academy, he was one of three philosophers sent to Rome in 155 BC where his lectures on the uncertainty of justice caused consternation among the leading politicians. He left no writings and many of his opinions are known only via his successor Clitomachus. He seems to have doubted the ability, not just of the senses but of reason too, in acquiring truth. His skepticism was, however, moderated by the belief that we can, nevertheless, ascertain probabilities of truth, to enable us to live and act correctly.

The Stoics used cognitive impressions as the basis by which truth could be perceived. Carneades argued that a cognitive impression could be in error because there were instances where entirely different objects or circumstances, such as identical twins or a mirror image, could produce identical cognitive impressions. In such cases, the only way to avoid error would be to suspend judgment. The Stoic counter-argument was that, without cognitive impressions, human beings would have no basis for making inquiries or acting. Carneades replied that such a basis could be found in “probable impressions.” Certain sense impressions would appear to be more convincing than others. If a sense impression is sufficiently convincing, and if it correlates with other relevant impressions, it can be used as a basis for action. There may be occasions when the sense impression is not accurate. When an important decision is to be made, particularly one relating to happiness, further inquiries can be made to verify the validity of the sense impression. In every instance, however, we are not dealing with absolute certainty; at best, however, we may experience 100% probability given a definite number of trials of experience; and, the greater the number of trials with the same outcomes, the stronger the grounds for belief; any and every counterexample would nonetheless weaken the grounds for belief.

To prove his point about the inability to determine absolute, unconditional truth, he demonstrated with great effect the logic of skepticism by delivering two contradictory orations on justice. One of these praised some justice, as a virtue grounded in nature; the other praised some injustice, on grounds of benevolent expediency. Although I don’t have any example from Carneades, I can think of many on my own. For example, it is unjust to take an old man’s cane; imagine, however, that a boy had fallen off a cliff and was holding onto a branch that was not only slightly out of your reach but also about to break from his weight; suppose further that you saw a cane that belonged to an old man, and despite not asking for permission to use it (which is unjust), you took the cane and used it to save the boys life. I don’t imagine that any reasonable person would disagree that in such a situation, such an injustice was good—especially if the old man in this story was not around to be asked for his permission to use his cane.