After a brief recent empirical sketch of Islamic finance, the paper turns to its main theoretical and conceptual purpose. It seeks to relate the concepts of Islamic and conventional finance, and to examine certain important questions which arise from the interaction between these systems. The paper is written from the perspective of conventional modern economics, as the authors are students of the latter. The paper discusses the main tenets of Islamic finance, as well as those of modern economics, including the implications of zero interest rates and those of Modigliani and Miller theorems. The most notable finding of this paper is that John Maynard Keynes’ analysis of employment, interest and money provides, inadvertently, the best rati...