Debt is part of the human condition. Civilization is based on exchanges - on gifts, trades, loans - and the revenges and insults that come when they are not paid back.
All Creatures know that some must die That all the rest may take and eat; Sooner or later, all transform Their blood to wine, their flesh to meat. But Man alone seeks Vengefulness, And writes his abstract Laws on stone; For this false Justice he has made, He tortures limb and crushes bone. Is this the image of a god? My tooth for yours, your eye for mine? Oh, if Revenge did move the stars Instead of Love, they would not shine.
Debt is not just a money thing. It's about owing and being owed. Money is just one thing you can exchange. You can exchange good deeds, you can exchange revenge, you can exchange murders.