In September 1935 the first International Congress for the Unity of Science took place at the Sorbonne in Paris with a large attendance by European as well as by a number of American scientists. Neurath, the moving force behind the conference, was also its leading light.¹ It proved to be a triumph for mid-European logical neopositivism and put Neurath's plan for a new "Encyclopedia" of scientific knowledge on an international footing.² From this point until his death at Oxford in 1945, the majority of his own writings were devoted to the problem of the encyclopedic integration of science, while his wider social and editorial energies were absorbed by the practical plan for an International Encyclopedia of Unified Science. Despite the obstacles presented in turn by the advent of National Socialism and by the outbreak of war, Neurath's project materialised, in 1935, in the foundation at the Hague of the International Institute for the Unity of Science³ and, from 1938, in the publication of Foundations of the Unity of Science under the auspices of the University of Chicago.⁴