"The strangest states of mind": chess, psychology and Emanuel Lasker's Kampf -- "Deeply rooted, yet alien" : Hungarian Jews and Mathematicians -- From Budapest to Göttingen: an apprenticeship in modern mathematics -- "The futile search for the perfect formula": Von Neumann's minimax theorem -- Equilibrium on trial: the Austrian interwar critics -- Wrestling with complexity: Wirtschaftsprognose and beyond -- Ethics and the excluded middle: Karl Menger and social science in interwar Vienna -- From austroliberalism to Anschluss: Morgenstern and the Viennese Economists in the 1930's -- Mathematics and the social order: Von Neumann's return to game theory -- Ars combinatoria: creating the Theory of games -- Morgenstern's catharsis -- Von Neumann's war -- Social science and the "present danger": game theory and psychology at the RAND Corporation, 1946--1960.