"Ellsberg's dissertation is a major landmark in the history of decision research. The issues that it raised and clarified have inspired scholars for decades, and will continue to do so." -- Daniel Kahneman, Princeton University
"I think a published version would be a valuable resource, not only as a historical document, but also for still fresh ideas." -- Dick Jeffrey, Princeton University
"Daniel Ellsberg set the world of decision theorists on its ear when he introduced the distinction between risk and ambiguity in his article excerpted from his dissertation. The clear convincing example caused a fundamental shift in thinking and in many ways led to the subsequent studies of decision and judgment by cognitive psychologists which, in turn, are having an increasing influence in the analysis of economic phenomena. It is good to have the complete text available to us at last." -- Kenneth J. Arrow, Stanford University, Emeritus