Thus also the virtues are causes to each other, because on account of their mutual correspondence they cannot be separated. And the stones in the arch are causes of its continuing in this category, but are not the causes of one another. And the teacher and the learner are to one another causes of progressing as respects the predicate.
And mutual and reciprocal causes are predicated, some of the same things, as the merchant and the retailer are causes of gain; and sometimes one of one thing and others of another, as the sword and the flesh; for the one is the cause to the flesh of being cut, and the flesh to the sword of cutting. [It is well said,] "An eye for an eye, life for life." For he who has wounded another mortally, is the cause to him of death, or of the occurrence of death. But on being mortally wounded by him in turn, he has had him as a cause in turn, not in respect of being a cause to him, but in another respect. For he becomes the cause of death to him, not that it was death returned the mortal stroke, but the wounded man himself. So that he was the cause of one thing, and had another cause. And he who has done wrong becomes the cause to another, to him who has been wronged. But the law which enjoins punishment to be inflicted is the cause not of injury, but to the one of retribution, to the other of discipline. So that the things which are, causes, are not causes to each other as causes.
It is still asked, if many things in conjunction become many causes of one thing. For the men who pull together are the causes of the ship being drawn down; but along with others, unless what is a joint cause be a cause.
Others say, if there are many causes, each by itself becomes the cause of one thing. For instance, the virtues, which are many, are causes of happiness, which is one; and of warmth and pain, similarly, the causes are many. Are not, then, the many virtues one in power, and the sources of warmth and of pain so, also? and does not the multitude of the virtues, being one in kind, become the cause of the one result, happiness?
But, in truth, Procatarctic causes are more than one both
