Between 1900 and 1930, social scientists attempted to refashion social ethics by conducting extensive social research. Some of them collaborated with Herbert Hoover before and after he became president. In the 1920s, they accepted positions on Herbert Hoover's various commissions. The work they did on these commissions made them a forum for manifesting their interest in modernizing social ethics. At one and the same time, they were in a position to define both social ethics and the purpose of the social sciences. Throughout this dissertation, I explore the cases of three social scientists involved with Hoover's commissions: the economist Wesley Clair Mitchell, the political scientist Charles Edward Merriam, and the industrial researcher and social worker Mary van Kleeck. Wesley Clair Mitchell addressed issues of American consumption and economic behaviour. Charles Edward Merriam analyzed the political behaviour of American citizens. Mary van Kleeck surveyed labour relations between American workers and employers. In this dissertation, I have employed methods developed by intellectual historians, focussing on the published and unpublished papers that these social experts and Herbert Hoover himself produced. This collaboration between Hoover and some of the most prominent social scientists of the day explains the ambitious project they undertook, that of adjusting social ethics to the modern living conditions they had discovered while carrying out their social research. In so doing, they sought to adapt the traditional code of conduct of most Americans to the new circumstances that prevailed in the first decades of the twentieth century