Alcaeus, as I said earlier, has come down to us only in fragments. We know "oinos kai alathea"--wine and truth--from an ancient scholar who wrote a commentary on Plato's
Symposium that was itself preserved in the margins of a later Plato manuscript. At 217e Alcibiades has just begun his wine-soaked encomium on Socrates, and uses the saying to justify the part of his tale that comes next. At this point the ancient scholar wrote:
paroimia oinos kai alathea, epi ton en methe ten aletheian legonton. esti de aismatos Alkaiou arche: oinos, o phile pai, kai alathea. kai Theokritos. ("The proverb "wine and truth" concerns those who tell the truth in their cups. It is the opening of a song of Alcaeus: Wine, my dear boy, and truth. And Theocritus uses it too.") [Fragment 366 Lobel-Page]
It is a sentiment that Alcaeus returned to a lot. We have it in another form [Fr. 333 Lobel-Page]:
oinos gar anthropoi dioptron ("for wine is a peephole into a man").
It passed down the generations of Greek poets. About a hundred years later Theognis of Megara uses it in one of his elegies, of which we have significant scraps, more than of Alcaeus [Theognis 500]:
andros d' oinos edeixe noon ("wine shows the mind of a man"). And 400 years after Theognis, as our scholiast points out, Theocritus of Syracuse uses it--in nearly its original form--to justify a poem in which he pours out his heart to a lover (
Idyll 29.1).
And 300 years after Theocritus the proverb finds its way into Pliny the Elder in the form
in vino veritas. As I said earlier, educated Romans of the wealthy class had been brought up on a diet of Greek authors, albeit mostly for the purpose of burnishing their oratorical skills (the Sophists won the debate, for the Romans). Those who weren't educated would still have heard of it indirectly: the first Latin tragedy was put on about 238 BC, written by Livius Andronicus, a Greek ex-slave. By the time we get to Pliny the Elder in the first century AD, the bulk of Greek literature had been digested into Latin one way or another.
skaioi=si me\n ga\r kaina\ prosfe/rwn sofa\
do/ceij a)xrei=oj kou) sofo\j pefuke/nai.
Euripides, Medea 298-299