Which rules for aggregating judgments on logically connected propositions are manipulable and which not? In this paper, we introduce a preference-free concept of non-manipulability and contrast it with a preference-theoretic concept of strategy-proofness. We characterize all non-manipulable and all strategy-proof judgment aggregation rules and prove an impossibility theorem similar to the Gibbard--Satterthwaite theorem. We also discuss weaker forms of non-manipulability and strategy-proofness. Comparing two frequently discussed aggregation rules, we show that “conclusion-based voting” is less vulnerable to manipulation than “premise-based voting”, which is strategy-proof only for “reason-oriented” individuals. Surprisingly, for “outcome-oriented” individuals, the two rules are strategically equivalent, generating identical judgments in equilibrium. Our results introduce game-theoretic considerations into judgment aggregation and have implications for debates on deliberative democracy.

List and Pettit have stated an impossibility theorem about the aggregation of individual opinion states. Building on recent work on the lottery paradox, this paper offers a variation on that result. The present result places different constraints on the voting agenda and the domain of profiles, but it covers a larger class of voting rules, which need not satisfy the proposition-wise independence of votes.

Fascination with the Coase Theorem arises over its apparently unassailable counterintuitive conclusion that the imposition of legal liability has no effect on which of two competing uses of land prevails, and also over the general difficulty in tying down an unqualified statement of the theorem. Instead of entering the debate over what exactly the theorem holds, this article suggests that the core of Coase's reasoning is flawed and to the extent that any version of the theorem relies upon this reasoning it can be disproved. The article commences by modelling the nature of the counter-intuitive thrust to the Coase Theorem, which is used to trace the development of Coase's reasoning, and ultimately to expose the flaw it contains. The heart of the article comprises the allegation of an error made by Coase when he transferred his core argument to the context of economic rents. Ancillary observations are made on the relationship between the Coasean analysis of characteristically legal problems and the conditions of general market equilibrium, and the theoretical status of Law-and-Economics.

Upon learning that John C. Harsanyi (1920–2000) was awarded the Bank of Sweden Prize in Economic Sciences in Memory of Alfred Nobel, in 1994, for his pioneering work in game theory, few economists probably questioned the appropriateness of that choice. The Budapest-born social scientist had already been recognized as a first-rank contributor to non-cooperative game theory for some time (see, e.g., Gul 1997). However, as many readers of this journal will be aware, Harsanyi first contributed to welfare economics, not game theory. More importantly, he was philosophically minded and accordingly has been “acknowledged as the most influential philosopher in economics” (Güth 1994: 252).1 This is of some significance since, before Harsanyi became acquainted with economics around 1950, his main interest was philosophy and, to a lesser extent, sociology and psychology. Rather than an economist with philosophical leanings, Harsanyi was actually a philosopher turned economist.

Philosophical errors are errors of a very peculiar nature.

Obviously, errors occur in the different areas of science, as well as in everyday life. But these errors are sooner or later recognized and exposed, and – most importantly – once they are recognized and exposed, they are essentially rendered harmless, at least for those versed in the respective discipline. A false historical datum, an experimental error or a calculation mistake becomes indefensible as soon as it is noticed.

The present note will be concerned only with Sir Partha Dasgupta's recent article in this journal (Dasgupta 2005). What is more, it will concentrate on those parts of the article which contain a serious misreading of Hilary Putnam's position on the entanglement of facts, theories and values. These philosophical matters can perhaps be clarified for economist readers (they should require no clarification for philosophers) by considering, to begin with, Dasgupta's interpretation of the Bergson–Samuelson position. What (Bergson) Burk (1938) and Samuelson (1947) were doing, according to Dasgupta, was to establish ‘the ethical foundations of the subject. . .over five decades ago’ (Dasgupta 2005: 221–2).2 Thus a major theme of the article is heard at once: economics is supposedly based on sound ethical foundations, and these can be traced (it is supposed) to specific work written long ago, and hence needing no augmentation. These ethical foundations, it is claimed, ‘are now regarded to be a settled matter’ (2005: 222).

Social thinkers frequently remind us that people differ on what constitutes personal well-being, but that even when they don't differ, they disagree over the extent to which one person's well-being can be permitted to be traded off against another's. They tell us that political differences are to be traced to differences in people's conceptions of personal and social well-being. We are given to understand, in other words, that people's ethics differ.

Without doubt, Weighing Lives, like its precursor, Weighing Goods, is an excellent and thought-provoking piece of work. In the first place, it addresses a question of the most fundamental importance, namely: how should we aggregate the well-being of past, present and future members of the human race under the various possible states of the world that may, in the event, prevail? This involves, amongst other things, dealing with questions of aggregation across time, people and different states of the world; the issue of what constitutes a “neutral” state of well-being (i.e., one neither better nor worse than not being alive) and what is, in fact, the value of continuing to survive.

It is not the job of philosophy to give direct practical advice either to people or to governments. Nevertheless, moral philosophy is immensely significant in practical matters. It influences the way we think and act, but only slowly as it filters through the process of public debate. I hope Weighing Lives will have a practical influence, but it is not meant to be a directly practical guide.