How do we get from the debt we owe the cosmos creating us to actual debts between people? By creating a system to calculate the specific debts we owe society through fines, fees, penalties, and debts to specific individuals. All the people “to whom we stand in a relation of ‘sin’ or ‘guilt'”.
Related note that I’m sticking in here: cattle is so often used as a currency by early societies because it was the most common sacrifice to the gods.
There’s lots of anthropological data on how stateless societies’ economies worked, but economists don’t like it because they used currency more for arranging relationships between people than they did for buying and selling things. Mostly they were used to “arrange marriages and settle disputes, particularly those arising from murders or personal injury.”
The phrase “to pay” comes from a word for “to pacify, appease”, meaning it’s about making up for something that pissed someone off. “To express just how badly you feel about having just killed his brother in a drunken brawl, and how much you would really like to avoid this becoming the basis for an ongoing blood-feud.”