Do We Need Theory to Study Disease?: lessons from cancer research and their implications for mental illness

This article applies general ideas from contemporary philosophy of science—chief among them that much good science proceeds without theories and laws—to the science of medicine. I claim that traditional philosophical debates over the nature of disease make demands on medicine that are mistaken. I demonstrate this philosophical error by applying the perspective of the philosophy of science to understanding the nature of disease in two concrete cases, cancer and depression. I first argue that cancer research produces various kinds of piecemeal causal explanation and does so without any well-developed theory of normal and malignant functioning, despite the rhetoric of some leading cancer researchers. I then defuse doubts about the scientific status of psychiatry, by demonstrating that it is not necessary to have a theory of normal functioning in order to understand and treat depression.