The Philosophy of Wealth. But now … he has reversed his position and build[s] up a body of economic laws based on competition" writes Homan (1928) and Everett (1946) finds: "Soon after writing The Philosophy of Wealth, however, Clark started to make defences for the competitive system. What caused the change is unknown. This much we can say. By the time he wrote The Distribution of Wealth he was convinced that pure competition was the natural and normal law by which the economic order obtained justice." One cause that prompted this reorientation could be the Haymarket Riot (1886) in Chicago when some strikers were shot and others hanged. In the US it resulted in a cleansing of higher education from socialist reformers and the ruin of the Knights of Labor. In 1888 Clark wrote Capital and Its Earnings. Frank A. Fetter later reflected on Bates' motivation for writing this work: The probable source from which immediate stimulation came to Clark was the contemporary single tax discussion. ... Events were just at that time crowding each other fast in the single tax propaganda. [ Henry George's ] Progress and Poverty... had a larger sale than any other book ever written by an American. ... No other economic subject at the time was comparable in importance in the public eye with the doctrine of Progress and Poverty. Capital and its Earnings "... wears the mien of pure theory .... But ... one can hardly fail to see on almost every page the reflections of the contemporary single-tax discussion. In the brief preface is expressed the hope that 'it may be found that these principles settle questions of agrarian socialism.' Repeatedly the discussion turns to 'the capital that vests itself in land,'... The foundation of Clark's further work was competition: "If nothing suppresses competition, progress will continue forever". Clark: "The science adapted … is economic Darwinism. … Though the process was savage, the outlook which it afforded was not wholly evil. The survival of crude strength was, in the long run, desirable". This was the fundament to develop the theory which made him famous: Given competition and homogeneous factors of production labor and capital, the repartition of the social product will be according to the productivity of the last physical input of units of labor and capital. This theorem is a cornerstone of neoclassical micro-economics. Clark stated it in 1891 and more elaborated