In the past few years, several population health and social epidemiology scholars have argued the need for better theory.^1–3 Given the comparatively underdeveloped social theoretical foundation for population health research, any progress in this area is reason for celebration. The glossary by Carpiano and Daley in this issue of JECH⁴ will help to reinforce and expand the awareness of the importance of theory in our work. Yet I would argue the theoretical project of population health is still in very early infancy and sadly, is still quite marginal to the main emphases of most publications in the field. Carpiano and Daley suggest that the need for theory is at least partly due to more interdisciplinary work, while I believe the main issue is between competing notions of what constitutes “explanation” and “theory” in science, which can vary as much within disciplines as it can between them. In the following few words, I use Carpiano and Daley’s glossary as a springboard for some additional thoughts about the theoretical foundations of population health research.

Given that “population health” is a vague term, it is worth briefly outlining what I consider its primary explanatory challenges to be, because it is to these challenges that a more theoretically informed population health research programme will have to rise. Population health stated plainly is a broad and complex field that must explain the systematic, differential distribution of health status by socioeconomic position. This enduring tendency, we know, holds across a wide variety of health conditions and disease states (from accidents …