Undoubtedly, some of the confusion is due to the lack of historical perspective.In other words, one must examine what is meant by mental illness and health at a given time, in a given place. This also involves a knowledge of the major physical, biological, and social theories which have prevailed from time to time with regard to the causation of mental illness. Action programmes are usually developed in terms of current concepts and theories of causation. And, in turn, the value judgements of society will determine, to a considerable degree, the emphasis placed on aetiological theories.