ABSTRACT
Almost all histories of psychology have a chapter on the early twentieth-century German controversy over thought psychology. The prominence given to this debate-usually under the slightly misleading title ‘imageless thought controversy’1-attests to the fact that it was one of the most decisive junctures in the history of psychology, and, thus, one of the key events in twentieth-century science. In the exchanges between the antagonists in this controversy many central parameters of the twentieth-century scientific study of human beings were identified, and some were permanently fixed. Topics covered in this debate were the nature of thought, its accessibility to observation and introspection, the role of experimentation in psychology, the relation between logic and psychology, and the differences between the natural and the social sciences.
