As with any complex theoretical formulation, analysis of the theoretical approach to the Depression taken in this work could begin with any of several causal links. We will, in this chapter, argue that a lack of new product innovation could have caused the declines in both the propensity to consume and desired investment which in turn were the proximate causes of the Great Depression. We will defer to Chapter 4 a detailed discussion of the time path of technological innovation during the interwar period. While we discuss consumption and investment in turn, we should note that factors which serve to depress consumption in a particular sector will naturally tend also to depress investment. We avoid repetition by discussing particular arguments under the most appropriate heading. In particular, while understanding of both consumption and investment requires a sectoral approach, we will perform a brief sectoral survey only under the investment heading.