In four volumes,  Foundational Papers in Complexity Science maps the development of complex-systems science through eighty-eight revolutionary works published across the twentieth century. Volume I spans the turbulent years from 1922 to 1962. Across several decades of war, runaway technological invention, and economic upheaval, complexity science emerges through the integration of ideas from evolution, computation, dynamics, and statistical physics. Included in this volume are essential papers by Léo Szilárd, Claude Shannon, Marvin Minsky, and Alan Turing. Each paper is introduced, and placed into its historical context, with enduring insights discussed by leading contemporary complexity scientists. Foundational Papers presents the first unified chart of the full territory of complexity science-an essential resource for navigating the modern world.