Search

The standard, Bayesian account of rational belief and decision is often argued to be unable to cope properly with severe uncertainty, of the sort ubiquitous in some areas of policy making. This paper tackles the question of what should replace it as a guide for rational decision making. It defends a recent proposal, which reserves a role for the decision maker’s confidence in beliefs. Beyond being able to cope with severe uncertainty, the account has strong normative credentials on the main fronts typically evoked as relevant for rational belief and decision. It fares particularly well, we argue, in comparison to other prominent non-Bayesian models in the literature.

We investigate how Activist Short Sellers (AShSs) expose publicly listed firms in an increasingly popular form of “research reports” openly denouncing alleged frauds, flawed business models, accounting irregularities, and wrongdoings. We focus on six AShSs that issued research reports that often led to a strong negative market reaction. Our empirical analysis exploits both qualitative and quantitative methods for a comprehensive dataset of 383 research reports targeting 171 unique firms, and three first-hand interviews with AShSs. Drawing on Aristotle’s rhetoric, we first examine how AShSs use narratives in striving to convince other investors that the target firms are overvalued. Specifically, we search the documents produced by AShSs for stylized narratives related to credibility-based (ethos), emotions-based (pathos), and logic-based (logos) rhetorical strategies. To assess the impact of these strategies, we examine the extent to which the AShSs’ rhetorical strategies resonate in 3,665 press articles. As expected, the press often refers to logos-based arguments. Interestingly, the press also brings up frequently pathos-based and ethos-based statements. Considering the importance of the press in shaping investors’ opinions, our study points to AShSs’ narratives playing a major role in policing financial markets. Theoretically, we show that AShSs, as dissenting market participants, produce narratives that go beyond the language of formal rationality – as they strive to reveal new information and frame it persuasively, in order to destabilize the extent of trustworthiness surrounding target firms.

Nudge is a concept of policy intervention that originates in Thaler and Sunstein's (2008) popular eponymous book. Following their own hints, we distinguish three properties of nudge interventions: they redirect individual choices by only slightly altering choice conditions (here nudge 1), they use rationality failures instrumentally (here nudge 2), and they alleviate the unfavourable effects of these failures (here nudge 3). We explore each property in semantic detail and show that no entailment relation holds between them. This calls into question the theoretical unity of nudge, as intended by Thaler and Sunstein and most followers. We eventually recommend pursuing each property separately, both in policy research and at the foundational level. We particularly emphasize the need of reconsidering the respective roles of decision theory and behavioural economics to delineate nudge 2 correctly. The paper differs from most of the literature in focusing on the definitional rather than the normative problems of nudge.

De tous les problèmes conçus par la théorie de la décision, le paradoxe d'Allais est peut-être celui qui aura suscité l'intérêt le plus persistant. La théorie y a consacré assez de travaux techniques remarquables pour qu'il soit désormais possible à l'histoire et à la philosophie des sciences de l'examiner réflexivement. Dans sa partie historique, l'article restitue le contexte d'apparition du paradoxe - le colloque de Paris, en 1952, auquel assistaient les principaux théoriciens de la décision du moment. L'axiomatique de von Neumann et Morgenstern en 1947 leur avait donné des raisons nouvelles d'approuver l'hypothèse de l'utilité attendue, et le contre-exemple d'Allais visait précisément à ébranler leur conviction. Les questions de la controverse étaient de type normatif, mais elles se perdirent quand le "paradoxe d'Allais" gagna tardivement la célébrité dans des travaux des années 1980 qui le traitaient comme une simple réfutation empirique. Ils en firent l'enjeu de "théories de l'utilité non-espérée" qu'ils développaient de même sous le seul angle empirique. Dans sa partie philosophique, l'article cherche à évaluer ce déplacement d'interprétation. D'un certain côté, les théoriciens de la décision firent bien de libérer leur travail expérimental des complications du normatif, car ils parvinrent ainsi à des résultats éclairants : l'hypothèse de l'utilité espérée était empiriquement réfutée, la responsabilité principale en revenait à l'axiome d'indépendance de von Neumann-Morgenstern, et l'étape suivante était de transformer adéquatement cet axiome. D'un autre côté, ils eurent tort de négliger un trait fondamental de leur domaine : les comportements observés ne sont informatifs que si les agents sont prêts à les assumer de manière réfléchie, c'est-à-dire à leur prêter une certaine valeur normative. D'après la reconstruction proposée ici, Allais ne voulait faire porter les expériences de choix que sur des sujets rationnels, ou bien sélectionnés au départ, ou bien révélés comme tels par l'expérience. L'article développe ces intuitions en revenant aux travaux des années 1970, aujourd'hui très peu connus, qui, sous l'influence d'Allais, proposèrent des traductions expérimentales de la rationalité, et il invite finalement la théorie de la décision à diversifier ses méthodes en s'inspirant de ces tentatives originales. Few problems in decision theory have raised more persisting interest than the Allais paradox. It appears that sufficiently many brilliant works have addressed it from within decision theory proper for history and philosophy of science now to enter stage. In its historical side, the paper recounts the paradox as it arose, i.e., in 1952, at a Paris conference attended by the main decision theorists of the time. They had drawn renewed confidence in expected utility theory (EUT) from the way von Neumann and Morgenstern had axiomatized it in 1947, and Allais devised his puzzle precisely to shaken their confidence. The issues between the two camps were normative, but they became lost in the developments of the 1980s that belatedly brought fame to the "Allais paradox". These works restricted the paradox to be a straightforward empirical refutation, turning it into a stake of also exclusively empirically oriented non-EU theories. In its philosophical vein, the paper tries to evaluate this shift of interpretation. To an extent, decision theorists were right because their experimental work was thus freed from a major complication and amenable to illuminating results: EUT was empirically refuted, the independence axiom of von Neumann and Morgentern was the main culprit, and the next theoretical stage was to modify this axiom appropriately. However, they were also wrong in not addressing an essential feature of their field, i.e., that observed behaviour is informative only if agents are prepared to endorse it reflectingly, i.e., to endow it with some normative value. As reconstructed here, Allais meant to reserve choice experiments to rational subjects, who were either selected at the outset, or identified as such by the experimental results. The paper tries to flesh out Allais's intuitions by turning to by now little known works of the 1970s, which under his influence provided experimental renderings of rationality, and it eventually suggests that decision theory might diversify its methods by taking inspiration from these original attempts.