"The difference between a debt and an obligation is that a debt can be precisely quantified. This requires money." Money makes debt possible, and emerge at the same moment in human history. A history of debt is a history of money.
Economists tell an imaginary story about the history of humans and money. In every economics textbook they claim that first we had barter, then money developed, and finally credits and debits.
But "The standard economic-history version has little to do with anything we observe when we examine how economic life is actually conducted, in real communities and marketplaces" 22
In reality we find everyone indebted to everyone else in a whole variety of ways, and most transactions take place without using currency.
Economists attribute three useful functions to money; as a way to exchange goods, as a way to store value, and as an accounting unit (keeping track of how much things are worth compared to other things)