This Special Issue marks the 100th anniversary of the first publication of two major books by economists on and around the themes of probability, risk and uncertainty: Frank Hyneman Knight’s Risk, Uncertainty, and Profit and John Maynard Keynes’ A Treatise on Probability. Knight’s book was written for economists, went on to become a classic within the discipline, and continues to be widely cited to this day on topics ranging from entrepreneurship to insurance design. Keynes’ book, in contrast, was written for a philosophical audience, initially ignored by economists save for a few early reviews, and subsequently overshadowed by his own magnum opus, The General Theory of Employment, Interest and Money, published in 1936. Yet the General The...