Existing theories have—by the consensus of the profession — failed to provide a convincing explanation of the entire Depression experience. In 1933, Morris Taylor wrote; “An impartial student will observe that there is some truth in nearly every suggested cause of depression, and in most of the proposed remedies.” Also in 1933, Irving Fisher recognized that existing theories all contained a grain of truth, but taken together left much unexplained. We take the same attitude here. We do not wish to demolish every theory, but merely to delineate their shortcomings and insights. From these we will be better able to develop a new theoretical structure which can fill in the gaps in our knowledge. Readers may wish to skim discussions of theories with which they are already familiar.