Abstract As it concerns both Man and the World, and it is interwoven with questions of order and balance, the notion of health deserves to be defined. But where can this definition be found? At first sight, it would seem to derive from medical science: an analysis of this type of approach, however, will reveal that the questions of physiology and pathology or the political and social questions of hygiene and prevention are favoured, and thus this notion will be rejected as non-functional. In linking biology, society and politic the social sciences lead to a less partitioned approach, without nevertheless being able to provide a satisfactory definition. To conclude, the need for a study of the evolution of the notion will be seen, which alon...