It is now accepted that many of the determinants of health and health care are social. This volume offers a philosophical and theoretical frame within which the nature and extent of this might be optimally examined. The analysis is rooted in Roy Bhaskar’s basic and dialectical critical realism, although it draws also on the critical theory of Jurgen Habermas. It purports to provide an ontologically and epistemologically grounded comparative sociology of contemporary health and health care in the twenty-first century. Carrying a fourfold agenda, the volume sets out a dialectical critical realist frame for a comparative sociology of health and health care; it clarifies sociology’s potential and limitations; it suggests a research programme and a series of questions for investigation; and it offers an argument for an action sociology embedded in a dialectical theory of transformative action. This volume will be of interest to students and scholars in the areas of philosophy, sociology and critical realism, as well as those working in health and social care.