This paper develops an “Economy of Peace” grounded in the Philosophy of Belonging, where being is belonging. It proposes that peace is not merely the absence of conflict but the result of institutional configurations that enable stable, inclusive, and dynamic belonging across economic, social, and political domains. Building on a stratified ontology (material, biological, and institutional) and dual temporality (synchronic structures and diachronic processes), the paper argues that economic systems capable of generating broad-based effective demand—particularly through the expansion of the middle class—are central to sustaining peaceful societies. The analysis integrates institutional economics, evolutionary perspectives, and macroeconomic dynamics to show that exclusionary systems generate structural instability, while inclusive belonging fosters cooperation, innovation, and long-term growth. The paper concludes by outlining policy principles for constructing “belonging-reliable” institutions as the foundation of durable peace.