This paper argues that the similarities between Ellsberg's and Shackle's frameworks for discussing the limits of the probabilistic approach to decision theory are more important than usually admitted. The paper discusses the grounds on which the ambiguity surrounding the decision-maker in...

In the insurance literature, it is often argued that private markets can provide insurance against ‘risks' but not against ‘uncertainties' in the sense of Knight (1921) or Keynes (1921). This claim is at odds with the standard economic model of risk exchange which, in assuming that...