So with my astonishment noted as yesterday., let me proceed on the subject of Islamic Finance. This is a set of practices (and accompanying theories) that have grown up to allow devout Muslims to make use of their savings, without keeping them in a mattress on the one hand and without committing the offense Muslims call riba on the other. Riba is often understood to mean contracted-for rates of interest on debt in general. How does finance work without interest? There are lots of ways to go about answering that question. I've recently read a book by Muhammad Akram Khan entitled What is Wrong with Islamic Economics? that holds among much else that rather too much ingenuity has been expended on trying to devise a system of finance without interest. The simple answer he prefers is that riba in the relevant sense is quite a narrow range of conduct, and completely distinct from the practice of charging for a borrower's access to investment capital. R...