verum tamen quid tibi ego videor in epistulis? nonne plebeio sermone agere tecum? nec enim semper eodem modo. quid enim simile habet epistula aut iudicio aut contioni? quin ipsa iudicia non solemus omnia tractare uno modo. privatas causas et eas tenuis agimus subtilius, capitis aut famae scilicet ornatius. epistulas vero cottidianis verbis texere solemus.
But, after all, what do you think of my style in letters? Don’t I talk with you in the vulgar tongue? Why, of course one doesn’t write always in the same style. For what analogy has a letter with a speech in court or at a public meeting? Nay, even as to speeches in court, it is not my practice to handle all in the same style. Private causes and such as are of slight importance we plead in simpler language; those that affect a man’s civil existence or reputation, of course, in a more ornate style: but letters it is our custom to compose in the language of everyday life.
(trans. E. Shuckburgh 1912)