Seneca, Epistulae ad Lucilium 1.10
“Thus it is, and I do not alter my opinion on this point: avoid the crowd, avoid the small gathering, avoid even one. There is no one with whom I would wish to share you. And just look at what opinion I have of you: I dare to trust you to yourself. They say that Crates, a student of the very same Silbo whom I mentioned in my last letter, once saw a man walking apart from the crowd and asked him what he was doing there alone. The man said, ‘I am talking with myself.’ Crates responded, ‘Please, note carefully: you’re talking with a wicked fellow.'”
Sic est, non muto sententiam: fuge multitudinem, fuge paucitatem, fuge etiam unum. Non habeo cum quo te communicatum velim. Et vide quod iudicium meum habeas: audeo te tibi credere. Crates, ut aiunt, huius ipsius Stilbonis auditor, cuius mentionem priore epistula feci, cum vidisset adulescentulum secreto ambulantem, interrogavit quid illic solus faceret. ‘Mecum’ inquit ‘loquor.’ Cui Crates ‘cave’ inquit ‘rogo et diligenter attende: cum homine malo loqueris’.