Explain the passage from David Graeber's book Debt: the first 5000 years, "Actually, the remarkable thing about the statement "one has to pay one's debts" is that even according to standard economic theory, it isn't true. A lender is supposed to accept a certain degree of risk. If all loans, no matter how idiotic, were still retrievable--if there were no bankruptcy laws, for instance--the results would be disastrous. What reason would lenders have not to make a stupid loan?"