>the interest must come from somewhere
This is one of the primary problems of the financial system according to Prof. Franz Hormann. In his banned TED Talk he explains that when money is created and loaned out by the central banks, the money to pay back the interest which is owed is never created, only the principal is created.
So basically we are not playing a zero-sum game. The money owed in the form of interest physically can never be paid because it does not exist, and this unpayable debt is what is shoved down to the bottom rungs of society and is what creates the "rat race". We are told we must work to pay off a debt that literally can never be paid off by default.