Carneades

Carneades (/kɑːrˈniːədiːz/; Greek: Καρνεάδης, Karneadēs, "of Carnea"; 214/3–129/8 BC) was a Greek philosopher, perhaps the most prominent head of the Skeptical Academy in Ancient Greece. He was born in Cyrene. By the year 159 BC, he had begun to attack many previous dogmatic doctrines, especially Stoicism and even the Epicureans, whom previous skeptics had spared.

As scholarch (leader) 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 leading politicians. He left no writings. His ideas were passed on to us through his successor Clitomachus whose own books were lost but relayed to us indirectly in the writings of Cicero and Sextus Empiricus. 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 (not in the sense of statistical probability, but in the sense of persuasiveness) of truth, to enable us to act.

According to Douglas Walton, Carneades' most important contribution to philosophy was his theory of plausibility based on reasonable evidence. The 3 criteria, as relayed by Empiricus, for accepting an argument, even if tentatively, is that it should be presented in a convincing way, that it is consistent with other arguments put forward, and that it can be confirmed by testing. Walton argues that Carneades provided a pragmatic response to skepticism by asserting that reasonable grounds were sufficient for action and belief in daily life rather than absolute certainty.