Moral Letters to Lucilius Section 17

Haec discenda, immo ediscenda sunt; non debet excusationes vitio philosophia suggerere. Nullam habet spem salutis aeger, quem ad intemperantiam medicus hortatur. Vale.

la tâche de la philosophie n’est point de suggérer des excuses au vice. Plus d’espoir de salut pour le malade que son médecin invite à l’intempérance.

You should learn such principles as these, nay rather you should learn them by heart; philosophy ought not to try to explain away vice. For a sick man, when his physician bids him live recklessly, is doomed beyond recall. Farewell.