Money gives us equivalence in the form of A = B, with two unlikes being equated by a price. But one never trusts that A really equals B; the buyer often fears he got cheated (why did the seller agree to hand it over for that price if he wasn't getting a good deal, a good deal at my expense?), the seller, that he got shorted (I surely could have gotten buyer to agree to more if he agreed so readily to that!). The price of silver might rise the next day, whereas eyes might suffer a glut and lose value.

But if I state my principle as a rule of identity, A = A, rather than of equivalence, A = B, then I can indulge the thought that I struck the balance exactly right. The price is a just price, an eye for an eye. We can smudge this too-pretty picture by worrying whether a blue eye equals a brown, a nearsighted one a 20–20 one, or the eye of a loser the eye of a person of honor. Still the rule as stated makes the poetic claim of identity, a powerful statement of getting the price exactly right.

Body Parts and Money

The classic statement of the talion mints some coin. It makes eyes into a form of money, or a money-like substance. First, eyes become the legal measure of the value of eyes, thus serving a crucial money function.