What Zippy Means by Non Secured Interest Bearing Lending

Zippy: As long as there's something actual real and not merely potential that's serving as the collateral, then the loan is okay. But charging interest on a loan that doesn't isn't secured in that way is wrong because you are essentially buying something that doesn't yet exist. And at the same time, you're basically enslaving the one who is borrowing from you Because he personally is fully responsible for repayment. He tries to map this distinction onto the medieval distinction between the mutual and the sociatas.