If you start from the barter theory of money, you have to resolve the problem of how and why you would come to select one commodity to measure just how much you want each of the other ones. If you start from a credit theory, you are left with the problem I described in the first chapter: how to turn a moral obligation into a specific sum of money, how the mere sense of owing someone else a favor can eventually turn into a system of accounting in which one is able to calculate exactly how many sheep or fish or chunks of silver it would take to repay the debt.
