In vino veritas
In vino veritas is a Latin phrase that means "In wine, there is truth", suggesting a person under the influence of alcohol is more likely to speak their hidden thoughts and desires. The phrase is sometimes continued as, "In vīnō vēritās, in aquā sānitās", i.e., "In wine there is truth, in water there is good sense (or good health)." Similar phrases exist across cultures and languages.
The expression, together with its counterpart in Greek, "Ἐν οἴνῳ ἀλήθεια" (En oinō alētheia), is found in Erasmus' Adagia, I.vii.17. Pliny the Elder's Naturalis historia contains an early allusion to the phrase. The Greek expression is quoted by Athenaeus of Naucratis in his Deipnosophistae; it is now traced back to a poem by Alcaeus.
Herodotus asserts that if the Persians decided something while drunk, they made a rule to reconsider it when sober. Authors after Herodotus have added that if the Persians made a decision while sober, they made a rule to reconsider it when they were drunk (Histories, book 1, section 133). The Roman historian Tacitus described how the Germanic peoples kept counsel at feasts, where they believed that drunkenness prevented the participants from dissembling.