Letters 108.38

They have been spoken by Plato, spoken by Zeno, spoken by Chrysippus or by Posidonius, and by a whole host of Stoics as numerous as excellent. I shall show you how men can prove their words to be their own: it is by doing what they have been talking about. Since therefore I have given you the message I wished to pass on to you, I shall now satisfy your craving and shall reserve for a new letter a complete answer to your summons; so that you may not approach in a condition of weariness a subject which is thorny and which should be followed with an attentive and painstaking ear. Farewell.

Seneca, Letters to Lucilius 108.38, translated by Richard Mott Gummere