Again, if we take the word unjust in the other sense, in which it is used to designate not general badness, but a particular species of vice, we find that in this sense also it is impossible to act unjustly to one’s self. (This, we found, is different from the former sense of the word: the unjust man in this second sense is bad in the same way as the coward is bad, i.e. as having a particular form of vice, not as having a completely vicious character, nor do we mean to say that he displays a completely vicious character when we say that he acts unjustly). For if it were possible, it would be possible for the same thing at the same time to be taken from and added to the same person. But this is impossible; and, in fact, a just deed or an unjust deed always implies more persons than one.

Further, an act of injustice, besides being voluntary, if not deliberate, must be prior to hurt received (for he who, having received some hurt, repays the same that he received is not held to act unjustly); but he who hurts himself suffers that very hurt at the same time that he inflicts it.