Current theories fall into two categories: 1, schizophrenia is an abnormal reaction pattern originating in early life; 2, it is organically determined, of unknown cause and obscure pathology. Lewis briefly reviews some of the historical highlights, and prevailing orientations in thinking about schizophrenia. Many writers stress the complexities of our civilization as important in its etiology. Among current productive types of research he mentions drug effects on the brain, neurological studies, brain extirpations, various forms of psychological investigation and Kallmann's studies of twins.