There is a story of Carneades of Cyrene, a post-classical philospher, who came to Rome as an ambassador of Athens. As a member of the New Academy, Carneades was well versed in sceptical argumentation, and stood steadfastly against dogma of any kind. Once in Rome he proceeded to deliver a spellbiding address, arguing that justice should top a list of human motives. The following he day, in service of his real argument concerning the uncertainly of human knowledge (deep scepticism), he proceeded to contradict the argument given the previous day, arguing instead that justice should rank much lower on the scale of human motives. Both declamations were more or less equally compelling. Cato the elder sent Carneades packing, presumably out of Cato’s concern that scepticism widely practised would undermine the Roman military culture and muddle popular thinking.
But somewhere I believe Dawkins is reported as having quipped that it is no bad thing to have an open mind, so long as it is not so open that one’s brains spill out. Doesn’t rationality require one to respect one’s evidence, which one cannot expect to do if one does not know what it is? Therefore, doesn’t one have to posit knowledge as unanalysable, in contrast to belief which may be true or false?