In the following pages we tell the story of how one financial theory − a Nobel Prize-winning theory accepted by almost everyone − enriched the world in the twentieth century but promises to diminish it in the twenty-first. We argue that Modern Portfolio Theory (MPT) and the investing philosophies built around it are showing their age. It is time to evolve. Such evolution is essential in order to improve and make sustainable finance’s ability to fulfill its twin main purposes: Providing adequate risk adjusted returns to investors and directing capital to where it is needed in the economy.