M. Tullius Cicero, For Sextus Roscius of Ameria
C. D. Yonge, Ed.

Moreover, consider now, O judges, the other matters, that you may see that no crime can be imagined with which that fellow has not disgraced himself. In less important matters, to deceive one's partner is a most shameful thing, and equally base with that which I have mentioned before. And rightly; because he who has communicated an affair to another thinks that he has procured assistance for himself. To whose good faith, then, shall a man have recourse who is injured by the want of faith in the man whom he has trusted? But these offences are to be punished with the greatest severity which are guarded against with the greatest difficulty. We can be reserved towards strangers; intimate friends must see many things more openly; but how can we guard against a companion? for even to be afraid of him is to do violence to the rights of duty. Our ancestors therefore rightly thought that he who had deceived his companion ought not to be considered in the number of good men.