Everyday practice would be simplified immeasurably by the formulation of a valid and acceptable explanation of the processes producing neurotic behavior. The very uniqueness of the individual who is further distinguished by peculiar hereditary and environmental determinants raises doubts from the beginning as to whether a single mechanism is responsible. This doubt should not, however, detract from the practical advantages of having a working hypothesis of functional illnesses since the parts will ultimately disclose the whole. To this end, varied theories have been proffered to stimulate further study.
Among the vital questions to be answered are what circumstances can produce or avoid development of neurotic illnesses and what are the factors which determine the exact symptomatology. The laboratory has provided little tangible assistance so far. W. B. Cannon demonstrated the physiologic effects of fear—a total response of the autonomic nervous system. This state is subjectively similar to an individual's response