The ancient Greeks and Romans must have been very good at keeping secrets. Or so our lack of information on the famous “Eleusinian Mysteries” (celebrated in an impressive sanctuary just a few miles outside Athens) would suggest – not to mention our lack of information on all the other, similar, initiatory religions found throughout the ancient world, from the ecstatic cult of Dionysus featured in Euripides’ Bacchae to the worship of the god Mithras by the Roman squaddies on Hadrian’s wall. There must have been literally hundreds of thousands, if not millions, of initiates, across the millennium of Classical history. And at Eleusis they included some of the most prominent (and garrulous) writers, thinkers and politicians of antiquity: Socrates and Plato, Hadrian and Marcus Aurelius, and many more. These cults are often set apart, by modern writers, from the calmer, less participatory, less emotional traditions of Graeco-Roman state religion. But we have no explicit ancient account of what the secret mysteries of any cult actually were, what happened at initiation or what exactly was revealed to the initiates. So far as we can now tell, there was hardly a leaky vessel among them; or, at any rate, whatever the gossip on the ancient street, there was no one who risked committing the religious secrets to writing and so sharing them with posterity.
more from Mary Beard at the TLS here.