Carneades

Carneades, who lived from 214 or 213 to 129 or 128 BC, was a Greek philosopher, perhaps the most prominent head of the Skeptical Academy in ancient Greece, born in Cyrene; by the time of his embassy to Rome in 155 BC he was already a leading critic of dogmatic doctrines, especially those of the Stoics and Epicureans, continuing the critical engagement his predecessor Arcesilaus had directed against both schools. As scholarch 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 of his own, and his ideas survive through his successor Clitomachus, whose books were in turn lost but relayed indirectly through the writings of Cicero and Sextus Empiricus. He appears to have doubted the ability of both the senses and reason to acquire certain truth, a skepticism moderated by the belief that people can nonetheless ascertain probabilities, in the sense of persuasiveness rather than statistics, sufficient to guide action; according to the scholar Douglas Walton, his most important contribution was a theory of plausibility based on reasonable evidence, holding that an argument merits provisional acceptance if it is presented convincingly, is consistent with other arguments, and can be confirmed by testing, offering what Walton calls a pragmatic response to skepticism grounded in reasonable grounds for everyday action and belief rather than absolute certainty.