If a man should suffer what he hath done, then there would be straightforward justice;”)
for in many cases differences arise: as, for instance, suppose one in authority has struck a man, he is not to be struck in turn; or if a man has struck one in authority, he must not only be struck but punished also.109 And again, the voluntariness or involuntariness of actions makes a great difference.
But in dealings of exchange such a principle of Justice as this Reciprocation forms the bond of union, but then it must be Reciprocation according to proportion and not exact equality, because by proportionate reciprocity of action the social community is held together, For either Reciprocation of evil is meant, and if this be not allowed it is thought to be a servile condition of things: or else Reciprocation of good, and if this be not effected then there is no admission to participation which is the very bond of their union.
And this is the moral of placing the Temple of the Graces (χάριτες) in the public streets; to impress the notion that there may be requital, this being peculiar to χάρις110 because a man ought to requite with a good turn the man who has done him a favour and then to become himself the originator of another χάρις, by doing him a favour.
Now the acts of mutual giving in due proportion may be represented by the diameters of a parallelogram, at the four angles of which the parties and their wares are so placed that the side connecting the parties be opposite to that connecting the wares, and each party be connected by one side with his own ware, as in the accompanying diagram.