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577Group Communication and the Transformation of Judgments: An Impossibility ResultJournal of Political Philosophy 19 (1): 1-27. 2011.While a large social-choice-theoretic literature discusses the aggregation of individual judgments into collective ones, there is much less formal work on the transformation of judgments in group communication. I develop a model of judgment transformation and prove a baseline impossibility theorem: Any judgment transformation function satisfying some initially plausible conditions is the identity function, under which no opinion change occurs. I identify escape routes from this impossibility and…Read more
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378Which worlds are possible? A judgment aggregation problemJournal of Philosophical Logic 37 (1). 2008.Suppose the members of a group (e.g., committee, jury, expert panel) each form a judgment on which worlds in a given set are possible, subject to the constraint that at least one world is possible but not all are. The group seeks to aggregate these individual judgments into a collective judgment, subject to the same constraint. I show that no judgment aggregation rule can solve this problem in accordance with three conditions: “unanimity,” “independence” and “non-dictatorship,” Although the resu…Read more
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323[This version of the paper has been superseded by "Reason-based choice and context-dependence: An explanatory framework", forthcoming in Economics & Philosophy.] We introduce a “reason-based” way of rationalizing an agent’s choice behaviour, which explains choices by specifying which properties of the options or choice context the agent cares about (the “motivationally salient properties”) and how he or she cares about these properties (the “fundamental preference relation”). Reason-based ration…Read more
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175The impossibility of a Paretian republican? Some comments on Pettit and SenEconomics and Philosophy 20 (1): 65-87. 2004.Philip Pettit (2001) has suggested that there are parallels between his republican account of freedom and Amartya Sen's (1970) account of freedom as decisive preference. In this paper, I discuss these parallels from a social-choice-theoretic perspective. I sketch a formalization of republican freedom and argue that republican freedom is formally very similar to freedom as defined in Sen's “minimal liberalism” condition. In consequence, the republican account of freedom is vulnerable to a version…Read more
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871Can there be a global Demos? An agency-based approachPhilosophy and Public Affairs 38 (1): 76-110. 2010.Can there be a global demos? The current debate about this topic is divided between two opposing camps: the “pessimist” or “impossibilist” camp, which holds that the emergence of a global demos is either conceptually or empirically impossible, and the “optimist” or “possibilist” camp, which holds that the emergence of a global demos is conceptually as well as empirically possible and an embryonic version of it already exists. However, the two camps agree neither on a common working definition of…Read more
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208On the significance of the absolute MarginBritish Journal for the Philosophy of Science 55 (3): 521-544. 2004.Consider the hypothesis H that a defendant is guilty, and the evidence E that a majority of h out of n independent jurors have voted for H and a minority of k:=n-h against H. How likely is the majority verdict to be correct? By a formula of Condorcet, the probability that H is true given E depends only on each juror's competence and on the absolute margin between the majority and the minority h-k, but neither on the number n, nor on the proportion h/n. This paper reassesses that result and explo…Read more
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107A model of path-dependence in decisions over multiple propositionsAmerican Political Science Review 98 (3): 495-513. 2004.I model sequential decisions over multiple interconnected propositions and investigate path-dependence in such decisions. The propositions and their interconnections are represented in propositional logic. A sequential decision process is path-dependent if its outcome depends on the order in which the propositions are considered. Assuming that earlier decisions constrain later ones, I prove three main results: First, certain rationality violations by the decision-making agent—individual or group…Read more
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35One fundamental thesis within the rapidly growing literature on deliberative democracy is that the stability and quality of a democracy depend not only on formal institutions such as the electoral system or the structure of parliamentary representation. They depend also on certain democratic competences of the citizens, especially their capacity for democratic communication. According to this thesis, above all the capacity for democratic deliberation, i.e., for argumentation, evaluation and for …Read more
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141Social choice theory and deliberative democracy : A response to AldredBritish Journal of Political Science 34 (4): 752-758. 2004.Jonathan Aldred shares our desire to promote a reconciliation between social choice theory and deliberative democracy in the interests of a more comprehensive and compelling account of democracy.1 His comments on some details of our analysis – specifically, our use of Arrow’s conditions of universal domain and independence of irrelevant alternatives – give us an opportunity to clarify our position. His discussion of the independence condition in particular identifies some ambiguity in our exposi…Read more
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407Independence and Interdependence: Lessons from the HiveRationality and Society 26 (2): 170-207. 2014.There is a substantial class of collective decision problems whose successful solution requires interdependence among decision makers at the agenda-setting stage and independence at the stage of choice. We define this class of problems and describe and apply a search-and-decision mechanism theoretically modeled in the context of honeybees and identified in earlier empirical work in biology. The honeybees’ mechanism has useful implications for mechanism design in human institutions, including cou…Read more
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1257The Methodology of Political TheoryIn Herman Cappelen, Tamar Gendler & John Hawthorne (eds.), The Oxford Handbook of Philosophical Methodology, Oxford University Press. 2016.This article examines the methodology of a core branch of contemporary political theory or philosophy: “analytic” political theory. After distinguishing political theory from related fields, such as political science, moral philosophy, and legal theory, the article discusses the analysis of political concepts. It then turns to the notions of principles and theories, as distinct from concepts, and reviews the methods of assessing such principles and theories, for the purpose of justifying or crit…Read more
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55Democracy in animal groups: a political science perspectiveTrends in Ecology and Evolution 19 (4): 168-169. 2004.This short paper proposes an application of Condorcet's jury theorem to animal group decisions.
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919The theory of judgment aggregation: an introductory reviewSynthese 187 (1): 179-207. 2012.This paper provides an introductory review of the theory of judgment aggregation. It introduces the paradoxes of majority voting that originally motivated the field, explains several key results on the impossibility of propositionwise judgment aggregation, presents a pedagogical proof of one of those results, discusses escape routes from the impossibility and relates judgment aggregation to some other salient aggregation problems, such as preference aggregation, abstract aggregation and probabil…Read more
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111Two concepts of agreementThe Good Society 11 (1): 72-79. 2002.This paper develops a distinction between "substantive agreement" and "meta-agreement" and explores the significance of this distinction for democracy and social choice.
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902Aggregating sets of judgments: Two impossibility results comparedSynthese 140 (1-2). 2004.The ``doctrinal paradox'' or ``discursive dilemma'' shows that propositionwise majority voting over the judgments held by multiple individuals on some interconnected propositions can lead to inconsistent collective judgments on these propositions. List and Pettit (2002) have proved that this paradox illustrates a more general impossibility theorem showing that there exists no aggregation procedure that generally produces consistent collective judgments and satisfies certain minimal conditions. A…Read more
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80Multidimensional welfare aggregationPublic Choice 119 119-142. 2004.Most accounts of welfare aggregation in the tradition of Arrow's and Sen's social-choice-theoretic frameworks represent the welfare of an individual in terms of a single welfare ordering or a single scalar-valued welfare function. I develop a multidimensional generalization of Arrow's and Sen's frameworks, representing individual welfare in terms of multiple personal welfare functions, corresponding to multiple 'dimensions' of welfare. I show that, as in the one-dimensional case, the existence o…Read more
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135Special majorities rationalizedBritish Journal of Political Science 36 (2): 213-241. 2006.Complaints are common about the arbitrary and conservative bias of special-majority rules. Such complaints, however, apply to asymmetrical versions of those rules alone. Symmetrical special-majority rules remedy that defect, albeit at the cost of often rendering no determinate verdict. Here what is formally at stake, both procedurally and epistemically, is explored in the choice between those two forms of special-majority rule and simple-majority rule; and practical ways are suggested of resolvi…Read more
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119Introduction to judgment aggregationJournal of Economic Theory 145 (2): 441-466. 2010.This introduces the symposium on judgment aggregation. The theory of judgment aggregation asks how several individuals' judgments on some logically connected propositions can be aggregated into consistent collective judgments. The aim of this introduction is to show how ideas from the familiar theory of preference aggregation can be extended to this more general case. We first translate a proof of Arrow's impossibility theorem into the new setting, so as to motivate some of the central concepts …Read more
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1150What is it Like to be a Group Agent?Noûs 295-319. 2015.The existence of group agents is relatively widely accepted. Examples are corporations, courts, NGOs, and even entire states. But should we also accept that there is such a thing as group consciousness? I give an overview of some of the key issues in this debate and sketch a tentative argument for the view that group agents lack phenomenal consciousness. In developing my argument, I draw on integrated information theory, a much-discussed theory of consciousness. I conclude by pointing out an imp…Read more
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84Group decisions in humans and animals: a surveyPhilosophical Transactions of the Royal Society B 364 719-742. 2009.Humans routinely make many decisions collectively, whether they choose a restaurant with friends, elect political leaders or decide actions to tackle international problems, such as climate change, that affect the future of the whole planet. We might be less aware of it, but group decisions are just as important to social animals as they are for us. Animal groups have to collectively decide about communal movements, activities, nesting sites and enterprises, such as cooperative breeding or hunti…Read more
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1256Nonreductive physicalism and the limits of the exclusion principleJournal of Philosophy 106 (9): 475-502. 2009.It is often argued that higher-level special-science properties cannot be causally efficacious since the lower-level physical properties on which they supervene are doing all the causal work. This claim is usually derived from an exclusion principle stating that if a higher-level property F supervenes on a physical property F* that is causally sufficient for a property G, then F cannot cause G. We employ an account of causation as difference-making to show that the truth or falsity of this princ…Read more
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232Dynamic and stochastic systems as a framework for metaphysics and the philosophy of scienceSynthese 198 (3): 2551-2612. 2021.Scientists often think of the world as a dynamical system, a stochastic process, or a generalization of such a system. Prominent examples of systems are the system of planets orbiting the sun or any other classical mechanical system, a hydrogen atom or any other quantum–mechanical system, and the earth’s atmosphere or any other statistical mechanical system. We introduce a general and unified framework for describing such systems and show how it can be used to examine some familiar philosophical…Read more
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98Collective Wisdom: Lessons from the Theory of Judgment AggregationIn J. Elster & H. Landemore (eds.), Collective Wisdom: Principles and Mechanisms, Cambridge University Press. 2012.Can collectives be wise? The thesis that they can has recently received a lot of attention. It has been argued that, in many judgmental or decision-making tasks, suitably organized groups can outperform their individual members. In this paper, I discuss the lessons we can learn about collective wisdom from the emerging theory of judgment aggregation, as distinct from the literature on Condorcet’s jury theorem.
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1032Three Kinds of Collective AttitudesErkenntnis 79 (S9): 1601-1622. 2014.This paper offers a comparison of three different kinds of collective attitudes: aggregate, common, and corporate attitudes. They differ not only in their relationship to individual attitudes—e.g., whether they are “reducible” to individual attitudes—but also in the roles they play in relation to the collectives to which they are ascribed. The failure to distinguish them can lead to confusion, in informal talk as well as in the social sciences. So, the paper’s message is an appeal for disambigua…Read more
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649Republican freedom and the rule of lawPolitics, Philosophy and Economics 5 (2): 201-220. 2006.At the core of republican thought, on Philip Pettit’s account, lies the conception of freedom as non-domination, as opposed to freedom as noninterference in the liberal sense. I revisit the distinction between liberal and republican freedom and argue that republican freedom incorporates a particular rule-of-law requirement, whereas liberal freedom does not. Liberals may also endorse such a requirement, but not as part of their conception of freedom itself. I offer a formal analysis of this rule-…Read more
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89A Note on Introducing a 'Zero-Line' of Welfare as an Escape-Route from Arrow's TheoremPacific Economic Review (Special Section in Honour of Amartya Sen) 6 (2): 223-238. 2001.Since Sen's insightful analysis of Arrow's Impossibility Theorem (Sen, 1970/1979), Arrow's theorem is often interpreted as a consequence of the exclusion of interpersonal information from Arrow's framework. Interpersonal comparability of either welfare levels or welfare units is known to be sufficient for circumventing Arrow's impossibility result (e.g. Sen, 1970/1979, 1982; Roberts, 1980; d'Aspremont, 1985). But it is less well known whether one of these types of comparability is also necessary…Read more
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223Scientists and philosophers frequently speak about levels of description, levels of explanation, and ontological levels. This paper presents a framework for studying levels. I give a general definition of a system of levels and discuss several applications, some of which refer to descriptive or explanatory levels while others refer to ontological levels. I illustrate the usefulness of this framework by bringing it to bear on some familiar philosophical questions. Is there a hierarchy of levels, …Read more
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105A simple proof of Sen's possibility theorem on majority decisionsElemente der Mathematik 60 45-56. 2005.Condorcet’s voting paradox shows that pairwise majority voting may lead to cyclical majority preferences. In a famous paper, Sen identified a general condition on a profile of individual preference orderings, called triplewise value-restriction, which is sufficient for the avoidance of such cycles. This note aims to make Sen’s result easily accessible. We provide an elementary proof of Sen's possibility theorem and a simple reformulation of Sen’s condition. We discuss how Sen’s condition is logi…Read more
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96Independence and interdependence in collective decision making: an agent-based model of nest-site choice by honey bee swarmsPhilosophical Transactions of the Royal Society B 364 755-762. 2009.Condorcet's classic jury theorem shows that when the members of a group have noisy but independent information about what is best for the group as a whole, majority decisions tend to outperform dictatorial ones. When voting is supplemented by communication, however, the resulting interdependencies between decision-makers can strengthen or undermine this effect: they can facilitate information pooling, but also amplify errors. We consider an intriguing non-human case of independent information po…Read more
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911Reason-based choice and context-dependence: An explanatory frameworkEconomics and Philosophy 32 (2): 175-229. 2016.We introduce a “reason-based” framework for explaining and predicting individual choices. It captures the idea that a decision-maker focuses on some but not all properties of the options and chooses an option whose motivationally salient properties he/she most prefers. Reason-based explanations allow us to distinguish between two kinds of context-dependent choice: the motivationally salient properties may (i) vary across choice contexts, and (ii) include not only “intrinsic” properties of the op…Read more
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Ludwig Maximilians Universität, MünchenMunich Centre for Mathematical Philosophy
Faculty of Philosophy, Philosophy of Science and Study of ReligionProfessor -
Munich, Bavaria, Germany