Conceptual/operational criteria of causality: relevance to systematic epidemiologic theory.

Emphasis has recently been placed on the possibility of developing "unified" criteria of causality applicable to both the infectious and chronic, non-infectious diseases. Yet, contemporary efforts are essentially compilations of criteria established over the past 140 years, without provision of the conceptual basis allowing such a unification. From hierarchical views of the natural history of infectious and neoplastic (i.e., chronic non-infectious) disease, it is possible to identify discipline and natural history-related concepts of causation from which it is possible to derive conceptual criteria of causality and complementary operational criteria of causality. These criteria are entirely relevant to the comprehension of disease as both product and process and applicable to both the infectious and neoplastic diseases.