Contemporary views hold that health and disease can be defined as objective states and thus should determine the design and delivery of health services. Yet health concepts are elusive and contestable. Health is neither an individual construction, a reflection of societal expectations, nor only the absence of pathologies. Based on philosophical and sociological theory, empirical evidence, and clinical experience, we argue that health has simultaneously objective and subjective features that converge into a dynamic complex-adaptive health model. Health (or its dysfunction, illness) is a dynamic state representing complex patterns of adaptation to body, mind, social, and environmental challenges, resulting in bodily homeostasis and personal internal coherence. The "balance of health" model-emergent, self-organizing, dynamic, and adaptive-underpins the very essence of medicine. This model should be the foundation for health systems design and also should inform therapeutic approaches, policy decision-making, and the development of emerging health service models. A complex adaptive health system focused on achieving the best possible "personal" health outcomes must provide the broad policy frameworks and resources required to implement people-centered health care. People-centered health systems are emergent in nature, resulting in locally different but mutually compatible solutions across the whole health system.