Nicomachean Ethics

​To some, reciprocal action seems to be unconditionally just, as the Pythagoreans claimed; for they defined the just unconditionally as reciprocal action toward another. But reciprocal action fits neither distributive justice nor corrective justice—though indeed they wish to mean this by the justice of Rhadamanthys too: “Should a man suffer what he did, right justice would be done”—for in many cases it disagrees; for example, if one holding office has struck, he ought not to be struck in return, and if one has struck an officer, he ought not only to be struck but also to be punished. Moreover, the voluntary and the involuntary differ greatly. But in exchange associations, this kind of justice holds them together—reciprocal action according to proportion and not according to equality. For it is by reciprocal action in proportion that the city remains together. For people seek either to return evil for evil, and if they cannot, it seems to be slavery; or to return good for good, and if they cannot, no sharing takes place, and it is by sharing that they hold together. Therefore they establish the temple of the Graces in a prominent place, so that there may be requital; for this is characteristic of grace (charis)—since one must return service to the one who was gracious, and in turn himself take the lead in being gracious again. And diagonal conjunction produces the reciprocal exchange according to proportion. Let the builder be A, the shoemaker B, the house C, and the shoe D. The builder must therefore receive from the shoemaker his work, and must himself share with him his own. If, then, there is first established the equal according to proportion, and then the reciprocal action takes place, what is mentioned will be achieved. But if not, it is not equal, and the association does not hold together; for nothing prevents the work of one from being better than that of the other, and so these must be equalized. This is the case with the other arts as well; for they would be destroyed if what the active factor produced in quantity and quality were not received by the passive factor in the same quantity and quality. For an association is formed not from two physicians, but from a physician and a farmer, and generally from those who are different and not equal; but these must be equalized. Therefore, all things that are exchanged must be in some way comparable. This is what money has been introduced for, and it becomes in a way a mean; for it measures all things, and therefore also excess and defect, such as how many shoes are equal to a house or to food. Therefore, as a builder is to a shoemaker, so must so many shoes be to a house or to food. For if this is not the case, there will be no exchange and no association; and this will not be, unless they are in some way equal. Therefore, all things must be measured by some single thing, as was said before. And this is in truth need, which holds all things together; for if people needed nothing, or not in the same way, there would either be no exchange or not the same exchange. But money has become by agreement a sort of representative of need; and for this reason it has the name “money” (nomisma), because it exists not by nature (physis) but by law or convention (nomos), and it is in our power to change it and make it useless. There will indeed be reciprocal action, when it is equalized, so that as a farmer is to a shoemaker, so is the work of the shoemaker to the work of the farmer. But they must not bring them into a form of proportion when they have already made the exchange (otherwise one extreme will have both excesses), but when they still have their own.