This Background Paper for the International Expert Working Group (IEWG) for a New Development Paradigm outlines the concept of well-being, flourishing, and happiness for all, which forms the objective of a new development paradigm. It seeks to synthesise for busy readers how the IEWG might explain and defend well-being and happiness, and also what value-added this work has in policy terms. The paper draws upon philosophical traditions to propose how the GNH concept of having nine domains of w...