Although Schumpeter made several attempts of elaborating and applying the basic model of the capitalist engine that he had presented in Entwicklung I and Development, the results of his major effort are found in Business Cycles. This book has roots back to his student years. At that time, members of the historical school (like Sombart and Spiethoff) had begun to focus on the problem of crises and cycles. Furthermore, this problem seems to have been a hot issue in Vienna among the participants in the seminars of the economic theoretician Böhm-Bawerk and the statistician and economic historian Inama-Sternegg. It is thus hardly surprising that Schumpeter put it at the top of his research agenda from the very beginning (see Section 5.4). However, he thereby not only set himself apart from the older generation of neoclassical economists who tended to ignore crises and cycles. It later became clear that his evolutionary theorising about business cycles was also radically different from the studies of business cycles that boomed in the 1920s and 1930s. The most obvious difference is that while nearly everybody else considered business cycles pathological, Schumpeter considered the phenomenon as part of the healthy process of economic evolution under capitalist conditions. Actually, his two-stroke model of the capitalist engine (see Figure 6.2 on page 149) suggested that waves are essential for capitalist economic evolution.