There is a well-known Latin phrase that says In vino veritas (in the wine is the truth), suggesting that under the influence of alcohol one is more predisposed to reveal things that one would not otherwise.
It is not something exclusive to the Romans, many other peoples have similar sayings, starting with the Greek phrase In oinoi aletheia which means more or less the same thing. And the Jewish Talmud also includes a passage about it.
We find the first allusion to the Roman expression in the Natural History (14, 141) of Pliny the Elder in the first century AD: volgoque veritas iam attribute vino est (truth is attributed to wine).
The Greek, although earlier and by the poet Alcaeus of Mytilene in the 6th century BC, we know it from a quote by the Byzantine scholar John Tzetzes in the 12th century, and he comes to say that wine is the window of man. And as for the Hebrew, much more explicit, that we find in the Talmud: the wine goes in, the secret comes out.
The disinhibiting properties of alcohol have been known for a long time, but surprisingly they were also used for something as opposite at first sight as making key decisions. Herodotus, when he talks about the Persians (in the 5th century BC) in the first book of his History states:
After well drunk, they usually deliberate about the most important business. What they then resolve, is proposed again by the master of the house in which they deliberated, a day later; and if the agreement seems good to them on an empty stomach, they put it into execution, and if not, they revoke it. They also tend to re-examine when they have drunk well that very thing on which they have deliberated in a state of sobriety (History I, CXXXIII)
That is, the decisions made while they were drunk were re-examined sober the next day, and if they still agreed that they were correct, they put them into practice. Apart from the fact that the system included a playful part that otherwise would not have decision-making, the Persians thus took advantage of the disinhibition produced by alcohol in the first debate to collect ideas (even those that might seem absurd).
In this way they ensured that all the participants exposed points of view that they would probably not dare to reveal when they were sober. The next day the debate would become more serious and, reexamining the issues they had drunkenly agreed on, they could consider options that would never have arisen had they not used this curious method.
However, Herodotus also mentions the opposite, which no longer seems so reliable. Making decisions while drunk, even when considering only sober approved ideas, certainly seems dangerous.
Perhaps what Herodotus means, in a somewhat convoluted way, is that the Persians wanted to be sure that their decisions were correct and so well founded that they could be valid under any state.
Curiously, Tacitus tells something similar but about the Germans in the first century AD:
And they also try at banquets to reconcile enemies, to have marriages, to choose princes, and, finally, many times about matters of peace and war; as if at no other time was the mind more capable of good and simple thoughts, nor more prompt and understood for great undertakings. And these people, who are not cunning or sagacious in themselves, still reveal the secrets of their chest with the license of amusement. In this way the intention of each one is exposed and as if exposed. The next day they deal with the same questions again, because they have consideration and respect for both times. They propose and vote when they do not know how to pretend, and they resolve and determine when they cannot err (Germania, XII)
According to Tacitus, the method allowed the Germans to free themselves from inhibitions and avoid the usual caution, thus leading to innovative solutions.
The Skeptical Philosopher / Uncorking the Past: The Quest for Wine, Beer, and Other Alcoholic Beverages (Patrick E.McGovern) / Herodotean Inquiries (S.Bernardete) / Wikipedia.