The concept of causality is reviewed with special emphasis on occupational diseases. Separate approaches from the philosophical, scientific, and legal points of view are identified. There is controversy over the methodology of logical causality; inductive and deductive methods are described and reference is made to the verification or refutation approach. Application of the methods to epidemiology are reviewed. It is likely that many diseases have multiple causes and that only a component of occupational causality can be identified in each patient. Methods of assigning such a component are discussed. The difficulties of developing an equitable compensation policy in such circumstances are reviewed. The possible benefits of proportional compensation are noted.