On Duties Passage 23

Fundamentum autem est iustitiae fides, id est dictorum conventorumque constantia et veritas. Ex quo, quamquam hoc videbitur fortasse cuipiam durius, tamen audeamus imitari Stoicos, qui studiose exquirunt, unde verba sint ducta, credamusque, quia fiat, quod dictum est, appellatam fidem. Sed iniustitiae genera duo sunt, unum eorum, qui inferunt, alterum eorum, qui ab iis, quibus infertur, si possunt, non propulsant iniuriam. Nam qui iniuste impetum in quempiam facit aut ira aut aliqua perturbatione incitatus, is quasi manus afferre videtur socio; qui autem non defendit nec obsistit, si potest, iniuriae, tam est in vitio, quam si parentes aut amicos aut patriam deserat.

The foundation of justice is good faith, that is, constancy and truth in words and agreements. From this, although it may perhaps seem somewhat strained to someone, let us dare to imitate the Stoics, who carefully investigate the origins of words, and believe that fides, good faith, was so named because what was said is done. There are two kinds of injustice: one belongs to those who inflict injury, the other to those who, although able, do not ward injury away from those upon whom it is inflicted. For one who unjustly attacks another, incited by anger or some other disturbance, seems as though he were laying hands upon a fellow human being. But one who does not defend another or resist injury when he can is as much at fault as if he were to abandon his parents, his friends, or his country.

Le fondement de la justice est la bonne foi, c’est-à-dire la constance et la vérité dans les paroles et les conventions. De là, bien que cela puisse sembler quelque peu forcé, osons imiter les stoïciens, qui recherchent soigneusement l’origine des mots, et croyons que fides, la bonne foi, est ainsi nommée parce que ce qui a été dit se fait. Il existe deux espèces d’injustice: celle de ceux qui commettent l’injustice, et celle de ceux qui, pouvant la repousser, ne défendent pas ceux qui la subissent. Celui qui attaque injustement quelqu’un, poussé par la colère ou quelque trouble, paraît en quelque sorte porter la main sur un associé. Mais celui qui ne défend pas une victime et ne s’oppose pas à l’injustice lorsqu’il le peut est aussi coupable que s’il abandonnait ses parents, ses amis ou sa patrie.