The Objective Standard article illustrates that historically usury was frowned upon by religion, however, was in high demand by everyone, because without it economy doesn't work. This dichotomy is easily resolved when you understand that religion is wrong, and there is no conflict.   In fact, this is very simple to understand: when I lend money, I can not use it for some purpose of my own -- in other words, lending, is a kind of service for those who borrow. For that, they pay a fee. It is only natural for this fee to be a percentage of the sum, since I loose a proportional amount of opportunities when I lend more money out. There really is nothing complicated about it. The article talks about historical perspective, in depth, and I highly recommend reading it.