[Determinism and indeterminism in the study of risk factors for disease]

In epidemiology "risk" is stated as a probability. This statement implies adopting a definite position regarding the concept of probability in science: whether it has to be intended as a lack of knowledge or a casual component of biological phenomena. On this fundamental premise the authors discuss the epidemiological implications on the issue of "determinism" of the recent developments of chemical, physical and biological sciences, particularly the quantum mechanics and the theories of complexity. The authors suggest three major interpretations of the relationship between risk factors and disease: strong determinism, weak determinism and dualism determinism/indeterminism. For each one of these positions they discuss the consistency, affinity and implications on epidemiological work.