Petrarch, Against a Certain Physician 2.43:
You could have hidden by being silent, but by speaking you cannot. The tongue is the door bolt of the mind, and I don’t know why you moved it when no one was knocking at the door, opening the shadowy and foul home of your heart to all, which would much better have remained closed, unless it was because it was difficult to hide your madness any longer. I think that you have never read where it is written, ‘The fool too, if he remains silent, will be thought wise; and if he but compress his lips, intelligent. Socrates was right when he had seen a certain decorous youth maintaining his silence and said, “Speak so that I can see you,” for he thought that a person was glimpsed not so much in their appearance as in their words.
Tacendo enim latere poteras, loquendo non potes. Lingua animi sera est; hanc tu, nullo ad ostium pulsante, nescio cur movisti, tenebricosam fedamque pectoris tui domum omnibus aperiens, que melius semper clausa mansisset, nisi quia dementiam diutius occultare difficile est. Credo non legeras quod scriptum est: “Stultus quoque si tacuerit, sapiens reputabitur; et si compresserit labia sua, intelligens”. Bene Socrates, cum decorum adolescentem tacitum vidisset, “Loquere” inquit “ut te videam”: non tam in vultu putabat videri hominem, quam in verbis.