A viable moral philosophy for a cosmopolitan world cannot be constructed from layers of intricate argumentation or rest on deep metaphysical or religious convictions. It must draw on simple, transparent principles that everyone can understand and agree upon. The ideal of human flourishing—that it’s good for people to lead long, healthy, happy, rich, and stimulating lives—is just such a principle, since it is based on nothing more (and nothing less) than our common humanity.
