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International audience; Social choice functions are generalized to handle Nash's independence of irrelevant alternatives. Possibility and impossibility results are established.

The main purpose of these comments on Phelps’s paper in the New York Review of Books is to indicate that the precedence of the good over the just and the pre-eminence at this time of growth and innovations in developed countries are debatable.

International audience; Kenneth J. Arrow’s contributions to knowledge in the twentieth century can only be compared with the contributions of giants such as Kurt Godel,Alan Turing or John von Neumann. It is on purpose that I write knowledge rather than economics because these contributions go well beyond economics to encompass political science, mathematics, operations research, and philosophy. I will restrict myself here to economics, only mentioning in passing the other domains. Regarding economics, the main contributions are his works on social choice theory, general economic equilibrium, individual choice theory, the treatment of uncertainty in general equilibrium models, and information theory. In particular, Arrow’s name is associated with two topics of paradigmatic importance for modern economics: the Arrow (im)possibility theorem and Arrow-Debreu equilibrium (along with Gerard Debreu)

La contribution de Kenneth Arrow a la connaissance est considerable et depasse les limites de la science economique. Nous ne pouvons comparer son apport qu'a celui de savants comme Alan Turing ou John von Neumann. Il est facile de constater que les travaux d'Arrow ont une influence en science politique, en mathematiques, en recherche operationnelle et en philosophie morale. Un aspect plus surprenant est l'importance de ces travaux en philosophie des sciences et en sciences de l'ingenieur. Nous allons ici nous concentrer sur l'apport a la science economique et ne mentionnerons les autres domaines qu'accessoirement. En ce qui concerne la science economique, les contributions essentielles sont, a notre avis, ses travaux sur le choix social, l'equilibre general, la theorie de la decision individuelle, le traitement de l'incertitude (en particulier dans les modeles d'equilibre) et la theorie economique de l'information. Une preuve, s'il en fallait, de l'importance de l'apport d'Arrow a la connaissance est le fait que son nom a ete associe a trois sujets particulierement importants de la science economique contemporaine : le theoreme d'(im)possibilite d'Arrow, la theorie de l'equilibre general a la Arrow-Debreu et la mesure d'Arrow-Pratt d'aversion pour le risque. (This abstract was borrowed from another version of this item.)

This paper is a survey of how economists and philosophers approach the issue of comparisons. More precisely, it is about what formal representation is appropriate whenever our ability to compare things breaks down. We restrict our attention to failures that arise with ordinal comparisons. We consider a number of formal approaches to this problem including one based on the idea of parity. We also consider the claim that the failure to compare things is a consequence of vagueness. We contrast two theories of vagueness; fuzzy set theory and supervaluation theory. Some applications of these theories are described.

Vagueness of preferences has been formalized by using the tools of fuzzy set theory, particularly in a quantitative context. Considering fuzzy aggregation (aggregation of lists of individual fuzzy preferences into a social fuzzy preference), Barrett, Pattanaik and Salles (BPS) showed that Arrow’s impossibility theorem and Gibbard’s oligarchy theorem were essentially preserved, given appropriate properties of fuzzy preferences and a sort of unrestricted domain condition. In a series of papers, we intend to analyze fuzzy aggregation in an economic environment. This means that the set of alternatives has some specific mathematical structure and preferences are, in some way, restricted. This first paper deals with the case where the set of alternatives are public goods, preferences exhibit various assumptions, in particular monotonicity assumptions, while BPS other assumptions are preserved. It is shown that according to which monotonicity assumptions are made, possibility results (given by the mean rule) or impossibility results prevail.

Serge-Christophe Kolm is a prominent member of the French community of ingenieurs-economistes (engineer-economists). Trained in the elite French grandes ecoles (great schools), these individuals, motivated by practical problems of the public sector, have made distinguished contributions to the study of normative eco nomics. Kolm, more so than others in this tradition, has had an ongoing interest in the philosophical foundations of normative economics, with the consequence that he has written extensively on social ethics.

One of the most justly famous result of social choice theory is Sen’s Theorem on the impossibility of a Paretian liberal. In two recent papers, Salles introduced the notion of limited rights both in an aggregation function framework and in a social choice function framework. He then proved Sen-type impossibility theorems. In the aggregation function framework an individual has a “right” if whenever she prefers an option (social state), say a, to another social state, say b, the social preference ranks a before b. Salles proposed to consider the following weakening. Rather than a being socially ranked before b, he suggests that b should not be ranked before a. The social choice framework is a framework which was introduced later than the aggregation function framework, but is thought to be more or less equivalent it. In this framework, if the individual prefers a to b, then b must not be chosen from any set to which a belongs. Salles’s weakening amounts to say that if it happens that b be chosen, then a must be chosen too. In the present paper, we will describe from an intuitive point of view the technical results obtained by Salles in the light of the distinction between possibility and obligation, and we will present a research program based on the use of tools borrowed from modal logic.

In this paper, we have investigated two subrelations of a domination relation which is the classical collective relation in voting games. These two subrelations, due to Gillies and Miller, have some nice properties; in particular, they are transitive. From these subrelations one can define obvious solution concepts by taking their maximal elements. If the set of social states is infinite, however, the existence of maximal elements is far from obvious, due to the lack of continuity. We have assumed that the set of social states was a compact metric space. We have adopted a measure-theoretic analysis. In the case of Gillies' subrelation, we have obtained very general existence theorems. In the case of Miller's subrelation (the uncovered set), though our theorem is still more general than what can be found in the literature, it is still far from being at the same level of generality.

In 1970 Amartya Sen introduced within social choice theory the notion of minimal liberty and proved an impossibility result concerning social decision functions. In this chapter Sen's condition of (minimal) liberty is weakened within the framework of social choice rules. It is then shown that the same kind of impossibility obtains for social choice functions.

1. An introduction to justice, political liberalism, and utilitarianism Marc Fleurbaey, Maurice Salles and John A. Weymark Part I. Themes from Rawls: 2. John Rawls's theory of justice: some critical comments John C. Harsanyi 3. Rawls, responsibility, and distributive justice Richard Arneson 4. Improving our ethical beliefs James Griffin Part II. Harsanyi's Impartial Observer and Social Aggregation Theorems: 5. Harsanyi's impartial observer is not a utilitarian John E. Roemer 6. Social aggregation and the expected utility hypothesis Charles Blackorby, David Donaldson and John A. Weymark 7. A welfarist version of Harsanyi's aggregation theorem Claude d'Aspremont and Philippe Mongin 8. Preference aggregation after Harsanyi Matthias Hild, Richard Jeffrey and Mathias Risse Part III. Goodness and Well-Being: 9. Can there be a preference-based utilitarianism? John Broome 10. Harsanyi, Rawls and the search for a common currency of advantage Robert Sugden 11. Utilitarianism versus fairness in welfare economics Marc Fleurbaey and Francois Maniquet 12. Rationality and want-satisfaction Brian Barry Part IV. Sharing the Gains from Social Cooperation 13. Naturalizing Harsanyi and Rawls Ken Binmore 14. The social contract naturalized Brian Skyrms 15. An alternative model of rational cooperation Edward F. McClennen Part V. Rights and Liberties: 16. Republican political theory Philip Pettit 17. Rule utilitarianism and liberal priorities Jonathan Riley.