This chapter examines health as complete well-being, focusing on the World Health Organization’s (WHO) definition and its philosophical underpinnings. The holistic concept is adequate to its goal, as it legitimizes the WHO’s expansive public health initiatives but faces criticism for being unattainable, ambiguous, and promoting medicalization. The chapter then shows that well-being is ambiguous—a “Babel” of definitions and measures—complicating its application across contexts. Philosophical theories—hedonism, desire-satisfaction, and flourishing—inform models of subjective and eudaimonic well-being, influencing tools like quality-adjusted life years (QALYs) and health-related quality of life (HRQoL). The chapter argues for conceptual clarity, suggesting a distinction between health (e.g., absence of disease) and well-being (e.g., flourishing), emphasizing the need for context-sensitive frameworks tailored to clinical, organizational, and policy goals.