 In the same German tradition and amidst the proliferation of work on energy physics and books on unity of science, the German energeticist Wilhelm Ostwald declared the 20th century the “Monistic century”. During the 1904 World’s Fair in St. Louis, the German psychologist and Harvard professor Hugo Munsterberg organized a Congress under the title “Unity of Knowledge”; invited speakers were Ostwald, Ludwig Boltzmann, Ernest Rutherford, Edward Leamington Nichols, Paul Langevin and Henri Poincaré. In 1911 the International Committee of Monism held its first meeting in Hamburg, with Ostwald presiding.[1] Two years later it published Ostwald’s monograph, Monism as the Goal of Civilization. In 1912, Mach, Felix Klein, David Hilbert, Einstein, and others signed a manifesto aiming at the development of a comprehensive world-view. Unification remained a driving scientific ideal. In the same spirit, Mathieu Leclerc du Sablon published his L’Unité de la Science (1919), exploring metaphysical foundations, and Johan Hjorst published The Unity of Science (1921), sketching out a history of philosophical systems and unifying scientific hypotheses.