Canguilhem criticized the concept of “public health”: health and disease are concepts that only apply to individuals, taken as organic totalities. Their extension to a different level of organization is purely metaphorical. The importance assumed by epidemiology in the construction of our knowledge of the normal and the pathological does, however, call for reflection on the role and the status of the population level of organization in our approach to health phenomena. The entanglement of the biological and the social in (...) human life and in contemporary societies justifies this level of analysis for better understanding the complexity and the interaction of health determinants both at the level of individuals and their interactions and at that of the population. But is this population level just a useful level of analysis that makes it possible to bring to light the social determinants of health at the individual level, or does it rest instead on characteristics of the population that are irreducible to individual characteristics, but which are nevertheless important for understanding and taking action with respect to both population and individual health? Defending this second alternative, I show how the epidemiological point of view, and in particular that of social epidemiology, leads us to rethink the possibility of a concept of “population health” that is not reducible to the sum of individual instances of health. (shrink)