“Surely one has to pay one’s debts.” The reason it’s so powerful is that it’s not actually an economic statement: it’s a moral statement. After all, isn’t paying one’s debts what morality is supposed to be all about? Giving people what is due them. Accepting one’s responsibilities. Fulfilling one’s obligations to others, just as one would expect them to fulfill their obligations to you. What could be a more obvious example of shirking one’s responsibilities than reneging on a promise, or refusing to pay a debt?