This volume?addresses the subject?of?uncertainty from the point of view of an extended conception of rationality. In particular, the?contributions explore the premises and implications of plausible reasoning when probabilities are non-measurable or unknown, and when the space of possible events is only partially identified.Fundamental Uncertainty and Plausible Reasoning: Introduction ; S.Marzetti & R.Scazzieri Logic, Empiricism and Probability Structures; H.Kyburg The Weight of Argument; I.Levi Inductive Intuition; V.Fano A Theory of Similarity and Uncertainty; R.Scazzieri Generalized Theory of Uncertainty: Principal Concepts and Ideas; L.Zadeh The Weight of Argument and Economic Decisions; A.Vercelli The Relevance Quotient and Probabilistic Equilibrium; D.Costantini & U.Garibaldi Non Self-Averaging Phenomena in Macroeconomics: Neglected Sources of Uncertainty and Policy Ineffectiveness; M.Aoki Induction and Atomic Universe: A Critical Reorientation of Keynes's Economic and Philosophical Thoughts; I.Hishiyama Uncertainty and Rationality: Keynes and Modern Economics; J.Kregel & E.Nasica Moral Good and Right Conduct: A General Theory of Welfare Under Fundamental Uncertainty; S.MarzettiSILVA MARZETTI DALL'ASTE BRANDOLINI is Professor of Economics, University of Bologna, Italy. She has published, amongst other research papers, 'Il comportamento razionale del policy maker', Economia Politica,1998; 'Economic and Social Demand for Coastal Protection',Coastal Engineering, 2005 (co-authored); 'Happiness and Sustainability: A Modern Paradox', in L. Bruni and P. L. Porta (eds), Handbook on the Economics of Happiness, Cheltenham, U.K. and Northampton, Mass., 2007; 'Recreational Demand Functions for Different Categories of Beach Visitors', Tourism Economics, 2009. She has also edited (in collaboration with A. Pasquinelli), John Maynard Keynes, Trattato sulla probabilit? (Italian translation of J. M. Keynes's A Treatise on Probability) and (in collaboration with R. Scl5