This paper outlines a conceptual framework for a sufficiency economy, defining sufficiency as the space between a generalizable notion of human wellbeing and ungeneralisable excess. It assumes an objective and universal concept of human needs to define a ‘floor’ and the concept of planetary boundaries to define a ‘ceiling’. This is set up as an alternative to the dominant preference satisfaction theory of value. It begins with a brief survey of the potential contributions of sufficientarianism and limitarianism to this endeavor (...) before outlining a theory of objective, universal human need. This recognizes the contextual variable nature of need satisfiers and the distinct methodology required to adjudicate necessities. It then turns to the planetary boundaries literature and utilizes a sequence of causal and normative reasoning to derive an operational ceiling and the concept of ungeneralisable luxuries. The final section addresses how the concepts of floors and ceilings might be operationalized via forms of dialogic democracy but noting the absence of any such institutions at the global level. Its policy conclusion is that a safe climate cannot be achieved through supply-side mitigation alone, and that fair demand-side mitigation necessarily requires a clear distinction between necessities and unnecessary luxuries, between which (hopefully) lies a space of sufficiency. (shrink)