In Chapter 12 of the General Theory, on “The State of Long-Term Expectation,” Keynes writes: “It would be foolish, in forming our expectations, to attach great weight to matters which are very uncertain”. In a footnote to this sentence, Keynes points out that by “very uncertain” he does not mean the same as “very improbable” and refers to the chapter on “The Weight of Arguments” in his earlier Treatise on Probability. The purpose of this article, in the first place, is (...) to provide an account of, and to sort out the relations between, Keynes's views on probability, uncertainty, and the weight of arguments. (shrink)

Ramsey's critique of Keynes's ‘logical’ approach to probability is widely regarded as decisive, and his own ‘subjective’ approach and SEU framework are now familiar tools in economics. This paper challenges the standard view of Ramsey's critique and assesses the SEU model from a Keynesian viewpoint on probability. It consists of a summary of the two theories and an evaluation of Ramsey's criticisms and alternative. The two main conclusions are that although Keynes yields to Ramsey on the question of the existence (...) of logical probability relations, the formal structure of his theory is compatible with non-objectivist interpretations of probability; and that Ramsey makes far heavier demands on the capacities of the ‘rational agent’ than does Keynes. (shrink)

Paul Davidson's critique of O'Driscoll and Rizzo is based on an “official” philosophical position that turns on an opposition between knowledge and ignorance and a corresponding opposition between ergodic and nonergodic processes. But Davidson's substantive analysis reveals a very different “unofficial” position, based on “sensible expectations” and a realist ontology of enduring social structures. While O'Driscoll and Rizzo have the edge on Davidson in terms of their characterization of agents’ beliefs, their ontology of event regularities is ultimately the same, and (...) suffers from the same drawbacks, as Davidson's official ontology. The solution to some of these problems may lie in adopting an ontology similar to the one Davidson invokes in his unofficial capacity. (shrink)

ABSTRACT What constitutes a Black Swan? And under what conditions may a Black Swan be expected to arise? As Nassim Taleb describes it, a Black Swan is an event that displays three key properties, the two most important of which are that: (1) it is not even imagined as a possibility prior to its occurrence; and (2) it is in some way significant in its impact. It follows that whether or not an event counts as a Black Swan depends on (...) the subjective imaginings of contemporaneous observers and their (usually implicit) criteria regarding what counts as a “significant impact.” Since there is nothing in determinism that precludes (1) and (2), Black Swans may occur even in a perfectly deterministic world. Nevertheless, if the world is indeed characterised by randomness, free will, emergence, and the like, then it is arguably more likely to throw forth events that display the above‐mentioned properties. The same goes for various specific features of an increasingly interconnected global economy, which allowed Taleb (paradoxically) to forecast what was, for most of us at least, the great Black Swan of 2008. (shrink)

ABSTRACT What constitutes a Black Swan? And under what conditions may a Black Swan be expected to arise? As Nassim Taleb describes it, a Black Swan is an event that displays three key properties, the two most important of which are that: (1) it is not even imagined as a possibility prior to its occurrence; and (2) it is in some way significant in its impact. It follows that whether or not an event counts as a Black Swan depends on (...) the subjective imaginings of contemporaneous observers and their (usually implicit) criteria regarding what counts as a “significant impact.” Since there is nothing in determinism that precludes (1) and (2), Black Swans may occur even in a perfectly deterministic world. Nevertheless, if the world is indeed characterised by randomness, free will, emergence, and the like, then it is arguably more likely to throw forth events that display the above‐mentioned properties. The same goes for various specific features of an increasingly interconnected global economy, which allowed Taleb (paradoxically) to forecast what was, for most of us at least, the great Black Swan of 2008. (shrink)

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 decision-makers are always guided by point-valued subjective probabilities, predicts that all uncertainties can, in theory, be insured. Supporters of the standard model argue that the insuring of highly idiosyncratic risks by Lloyd's of London proves (...) that this is so even in practice. The purpose of this article is to show that Bruno de Finetti, famous as one of the three founding fathers of the subjective approach to probability assumed by the standard model, actually made a theoretical case for uncertainty within the subjectivist approach. We draw on empirical evidence from the practice of underwriters to show how this case may help explain the reluctance of insurers to cover highly uncertain contingencies. (shrink)

A recurring theme in discussions about the uncertainties of belief is their connection with the uncertainties of chance. Economists, broadly speaking, fall into two groups on this issue. One holds that beliefs can only be taken to correspond to point probabilities in situations that approximate games of chance. The other holds that beliefs should be treated as point probabilities, entering economics via decision theory and emerging as the parameters of consistent choice. I shall call these the traditional view and the (...) Bayesian view respectively. (shrink)

Examines ontological presuppositions that inform traditional and Bayesian positions on the uncertainties of belief in economic theory. D. Knight and J.M. Keynes’ views on the risks and uncertainties in economics; Reasons for the popularity of the Bayesian view in modern economic theory.