Aeneas Silvius Piccolomini, de Educatione Liberorum XXXV
(See also Aulus Gellius 1.15, from which most of this is shamelessly ripped; and also this):
“What then should we say, considering that there is great utility in both silence and in speaking? We would have you hold to the middle course, and find yourself neither always speaking nor always quit. I do not demand a five-years silence in the Pythagorean fashion, nor would I recommend the loquacity of a Thersites. The ancients used to say that the tongue should not always be free and wandering, but moved and perhaps even governed by chains rooted deep in the heart and soul. The words of those who speak freely, lightly, aimlessly, and with no sense of timing ought to be considered as springing not from the heart, but from the mouth itself. Homer, however, says that Ulysses – a man endowed with wisdom and eloquence – would speak not from his mouth, but from his heart. Certainly, the ‘bulwark of the teeth’ is placed as a restraint on inconsiderate speech, so that temerity in speaking would not be checked only by the heart’s guardianship, but also be hedged in by guards placed in the mouth. One should take care not to deserve that charge of Epicharmus, of being a man ‘who, although he was unable to speak, yet could not be silent,’ or even that of Sallust, who speaks of one who ‘when he spoke was talkative rather than eloquent.’”
Quid ergo dicemus, cum et silentii et orationis magna utilitas sit? Tenere te medium volumus, neque tacere semper neque loqui semper. Non exigimus Pythagoreum illud quinquennale silentium neque Thersitis loquacitatem. Linguam dicebant veteres debere non esse liberam nec vagam sed vinculis de pectore imo ac de corde aptis moveri et quasi gubernari. Nam qui sunt faciles, leves, futiles et importuni locutores, horum orationem bene aestimatum in ore nasci, non in pectore. Ulixem contra Homerus sapienti facundia praeditum vocem mittere ait non ex ore, sed ex pectore. Nempe verborum coercendae petulantiae vallum positum est dentium, ut loquendi temeritas non cordis tantum custodia cohibeatur, sed et quibusdam quasi excubiis in ore positis saepiatur. Cavendum est, ne obiici possit illud Epicharmi, ‘<qui> cum loqui non posset, tacere non potuit,’ aut Sallustianum: ‘loquax inquit magis quam facundus.’
