M. Tullius Cicero Pro P. Sulla 10

[10] “You gave evidence against Autronius,” says he, “and you are defending Sulla.” All this, O judges, has this object to prove that if I am an inconstant and fickle-minded man, my evidence ought not to be credited, and my defence ought not to carry any authority with it. But if there is found in me a proper consideration for the republic, a scrupulous regard to my duty, and a constant desire to retain the good-will of virtuous men, then there is nothing which an accuser ought less to say than that Sulla is defended by me, but that Autronius was injured by my evidence against him. For I think that I not only carry with me zeal in defending causes, but also that my deliberate opinion has some weight; which, however, I will use with moderation, O judges, and I would not have used it at all if he had not compelled me.