All human interactions are not forms of exchange. Only some are. Exchange encourages a particular way of conceiving human relations. This is because exchange implies equality, but it also implies separation. It’s precisely when the money changes hands, when the debt is canceled, that equality is restored and both parties can walk away and have nothing further to do with each other. Debt is what happens in between: when the two parties cannot yet walk away from each other, because they are not yet equal. But it is carried out in the shadow of eventual equality.
