In Osama Bin Laden’s latest screed, one of the things he exhorts people to do is give up interest. The charging and paying of interest is forbidden in strict Islam. Known as riba (increase), it was the subject of some of Mohammed’s most vehement condemnations. One can see why with only a cursory look at history. Namely, moneylending was largely an uncontrolled practice that guaranteed a class structure that could not be broken, incurred debts that led to involuntary servitude, and was an all around nasty way to keep the serfs in the fields. Mohammed, rather than suggesting some form of regulation, vented spleen and condemned it outright.  Christians, of course, had their own attitude toward it, which led to out-groups being the only ones allowed to lend money (Jews, famously, but not exclusively). The prohibition was based mainly on two Biblical passages (both Old Testament): Leviticus 25:36–37 (“Take thou no usury…”) and Ezekiel 18:13 (“He that have give forth usury, and hath taken increase: shall he live? He shall not live…”).

The Catholic Church used to excommunicate moneylenders. The law said: Quidquid sorti accedit, usura est “what exceeds the principal is usury.” (The Italian Renaissance, aside from great art and a few geniuses, also revolutionized banking. The bankers noted that this applied only to loans, not contracts, so they erected a facade behind which they could do exactly what they wanted. They made no loans. They traded in Bills of Exchange. Technically, it was a sale of one …