Public health researchers, policy makers, and practitioners agree that health is the outcome of interactions between biological, behavioral, and social determinants. Nonetheless, institutional patterns of research funding and practice remain obstacles to generating research at and between each of these levels. These practices are embedded in historic assumptions about the nature of reality and how it can best be understood. Current debates over the criteria for evaluating public health research have centered on the applicability of the clinical evidence-based medicine (EBM) model to the field of public health. The EBM hierarchy, which is based on traditional scientific assumptions about causality, is insufficient and potentially harmful as the basis for evaluating research on the determinants of health. Yet those who have put forward a critique of EBM have failed to develop a plausible alternative. Critical realism, based on the philosophy of Roy Bhaskar, may provide a way out of the current stalemate, enabling public health researchers from various disciplines and research paradigms to work together, bringing the full weight of scientific knowledge to bear on increasingly complex and global public health problems.