Reasons and Rationality

This paper is a response to ‘Why Be Rational?’ by Niko Kolodny. Kolodny argues that we have no reason to satisfy the requirements of rationality. His argument assumes that these requirements have a logically narrow scope. To see what the question of scope turns on, this comment provides a semantics for ‘requirement’. It shows that requirements of rationality have a wide scope, at least under one sense of ‘requirement’. Consequently Kolodny's conclusion cannot be derived.

In the theory of judgment aggregation, it is known for which agendas of propositions it is possible to aggregate individual judgments into collective ones in accordance with the Arrow-inspired requirements of universal domain, collective rationality, unanimity preservation, nondictatorship and propositionwise independence. But it is only partially known for which agendas it is possible to respect additional requirements, notably non-oligarchy, anonymity, no individual veto power, or implication preservation. We fully characterize the agendas for which there are such possibilities, thereby answering the most salient open questions about propositionwise judgment aggregation. Our results build on earlier results by Nehring and Puppe (2002), Nehring (2006) and Dietrich and List (2007a).

Preference aggregation and judgment aggregation are two basic research models of group decision making. And preference aggregation has been deeply studied in social choice theory. However, researches of social choice theory gradually focus on judgment aggregation which appears recently. Judgment aggregation focuses on how to aggregate many consistent logical formulas into one, from the perspective of logic. We try to start with judgment aggregation model based on logic and then explore different solutions to problem of judgment aggregation.

Judgment aggregation is a field in which individuals are required to vote for or against a certain decision (the conclusion) while providing reasons for their choice. The reasons and the conclusion are logically connected propositions. The problem is how a collective judgment on logically interconnected propositions can be defined from individual judgments on the same propositions. It turns out that, despite the fact that the individuals are logically consistent, the aggregation of their judgments may lead to an inconsistent group outcome, where the reasons do not support the conclusion. However, in this paper we claim that collective irrationality should not be the only worry of judgment aggregation. For example, judgment aggregation would not reject a consistent combination of reasons and conclusion that no member voted for. In our view this may not be a desirable solution. This motivates our research about when a social outcome is `compatible' with the individuals' judgments. The key notion that we want to capture is that any individual member has to be able to defend the collective decision. This is guaranteed when the group outcome is compatible with its members views. Judgment aggregation problems are usually studied using classical propositional logic. However, for our analysis we use an argumentation approach to judgment aggregation problems. Indeed the question of how individual evaluations can be combined into a collective one can also be addressed in abstract argumentation. We introduce three aggregation operators that satisfy the condition above, and we offer two definitions of compatibility. Not only does our proposal satisfy a good number of standard judgment aggregation postulates, but it also avoids the problem of individual members of a group having to become committed to a group judgment that is in conflict with their own individual positions.

Judgment aggregation is a mathematical theory of collective decision-making. It concerns the methods whereby individual opinions about logically interconnected issues of interest can, or cannot, be aggregated into one collective stance. Aggregation problems have traditionally been of interest for disciplines like economics and the political sciences, as well as philosophy, where judgment aggregation itself originates from, but have recently captured the attention of disciplines like computer science, artificial intelligence and multi-agent systems. Judgment aggregation has emerged in the last decade as a unifying paradigm for the formalization and understanding of aggregation problems. Still, no comprehensive presentation of the theory is available to date. This Synthesis Lecture aims at filling this gap presenting the key motivations, results, abstractions and techniques underpinning it.

There are two different fundamental conceptions of the task of social aggregation: interest aggregation and judgment aggregation. While the former aims at the fair and efficient trade-off of personal interests, the latter aims the best resolution of disagreement. Both are possible interpretations of the standard preference aggregation and preference-based voting problems. This note makes two broad points. First, the judgment aggregation conception is not yet well understood and remains undertheorized. Second, the difference between the two conceptions matters; it is a difference that makes a difference. To substantiate the first point, we argue that judgment aggregation as resolution of disagreement cannot be subsumed under statistical aggregation in the manner of Condorcet’s jury theorem, and sketch a more specific articulation as “reflexive consensus under arguable disagreement”. To substantiate the second point, we illustrate the difference in the context of two important voting rules, the Kemeny rule and Majority Judgment.

Judgment aggregation is a recent theory that combines aggregation problems previously studied by social choice theory with logic. Social choice theory is a vast subject, including not only the study of preference aggregation and voting theory but also topics like social welfare and justice. Given the tight links between judgment aggregation and preference aggregation, in this first chapter we give a concise survey on some historical aspects of preference aggregation and then introduce and motivate the more recent field of judgment aggregation. The chapter builds on [Sen99, Sen86, Bla58] for the historical overview on social choice theory, and on [KS93, Kor92] for the informal introduction to judgment aggregation.

Judgment aggregation problems form a class of collective decision-making problems represented in an abstract way, subsuming some well known problems such as voting. A collective decision can be reached in many ways, but a direct one-step aggregation of individual decisions is arguably most studied. Another way to reach collective decisions is by iterative consensus building – allowing each decision-maker to change their individual decision in response to the choices of the other agents until a consensus is reached. Iterative consensus building has so far only been studied for voting problems. Here we propose an iterative judgment aggregation algorithm, based on movements in an undirected graph, and we study for which instances it terminates with a consensus. We also compare the computational complexity of our itterative procedure with that of related judgment aggregation operators.

Complexity of manipulation and bribery in premise-based judgment aggregation with simple formulas

An allocation problem is a type of aggregation problem in which the values of individuals' opinions on some set of variables (canonically a set of mutually exclusive and exhaustive possibilities) sum to a constant. This paper shows that for realistic allocation problems, namely ones in which the set of possible opinion values is finite, the only universal aggregation methods that satisfy two commonly invoked conditions are the dictatorial ones. The two conditions are, first, that the aggregate opinion on any variable depends only on the individuals' opinions on that variable and not on their opinions on any other variable and, secondly, that the aggregate opinion minimally preserves unanimous individual opinion. Connections between this result and similar ones in the literature on judgment aggregation are explored and their significance assessed.

Historically, the reasons behind the pseudonym have been both brutal and mild, ranging from the political safeguards against being killed for your subversions, to the merely social, when you didn't want the king's court, or your relatives around the corner, to know what you wrote. Or you craved to be a child of the people, though by birth an aristocrat. Or if female, you felt yourself to be less than a Sappho, yet more than a Miss Reade.-Hortense CalisherI. Fiction.It appears self-evident that no ethical issues arise from the pseudonymous publication of genuine fiction-since works of fiction state no claims. This intuition is bolstered by the apparent fact that no recent author1 has had serious difficulties-beyond eventual exposure-because of the use of this hoary literary device. Moreover, such issues as I may not have considered are outside the scope of this journal since fiction is not information in any straightforward sense, whatever deeper truths it may convey. Moreover, I suspect that such ethical issues as might arise do so in cases where the fiction is not what we would call genuine fiction. It is, of course, arguable whether there is any such thing as genuine fiction, or whether everything ever penned by man somehow derives from personal experience-regardless, the inverse function by which the personal experiences involved in the creation of a work of fiction can be recovered from its text is so complicated as to be beyond anyone but a couchman or a certain type of critic.II. Nonfiction.Nonfiction is quite another matter. If the classical question in the political context is cui bono?, the two questions that immediately present themselves when a pseudonym is used are, (a) From whom does the author hide? and (b) What does the author hide-beyond his identity and behind his pseudonymous identity?A. From whom does the author hide?The author may be concealing his identity from his family, friends, and acquaintances (if, say, he is advocating a position on a sexual issue in which he believes, about which he is not ashamed, but which would cause him considerable embarrassment, a rather different matter), from his employer and coworkers (if, say, he is advocating a position his company has strenuously rejected in court filings), from his industry (if, say, he is advocating a position against which the industry as a whole is feverishly lobbying), from his professional colleagues (if, say, he is on the masthead of a number of magazines that have a certain general outlook, and he is, in this instance, deviating substantially from orthodoxy), from the government or organized crime (if, say, he has a reasonably justified fear of unjustified prosecution or investigation-or a hit). These are among the many ethically justified deceived. The one group it is, in general, unethical to deceive-the only group to which the author has a commitment qua author-is his audience, his readers, those for whom he writes. While his family, friends, acquaintances, employer, co-workers, industry, colleagues, the state, and the mob may come to learn of his writing, as long as they are not his intended audience (as indicated, in part, by the venue), no duty has been breached and no commitment violated.This simple rule clears most legitimate uses of pseudonymous publication of nonfiction, although it leaves open the difficult-genuinely difficult-question as to whether an author may pseudonymously address the very audience from which he seeks to conceal his identity, for fear of repercussions. I do not think the answer to this question can be formulated by a rule, even by one that is complex and multi-partite. That is why I call it genuinely difficult: Each individual case requires wisdom and judgment-and, I would advise, consultation with at least two trusted others whose inner moral compasses have been found to be true in the past. I would also add-in warning, and would be remiss if I failed to do so-the purely pragmatic point that the veil of pseudonymity is much more easily pierced than one might naively suppose, and should that occur, the repercussions will invariably be even more severe. …

We deal the problem of aggregation of individual judgments for a global evaluation of a candidate or a product. In our theoretically oriented approach, aggregation operators are compared with each other based on their mathematical properties. We show that any monotone and strategy-proof operators is characterized by a particular collection of decision makers.

How can several individuals’ probability assignments to some events be aggregated into a collective probability assignment? Classic results on this problem assume that the set of relevant events—the agenda—is a sigma -algebra and is thus closed under disjunction (union) and conjunction (intersection). We drop this demanding assumption and explore probabilistic opinion pooling on general agendas. One might be interested in the probability of rain and that of an interest-rate increase, but not in the probability of rain or an interest-rate increase. We characterize linear pooling and neutral pooling for general agendas, with classic results as special cases for agendas that are sigma -algebras. As an illustrative application, we also consider probabilistic preference aggregation. Finally, we unify our results with existing results on binary judgment aggregation and Arrovian preference aggregation. We show that the same kinds of axioms (independence and consensus preservation) have radically different implications for different aggregation problems: linearity for probability aggregation and dictatorship for binary judgment or preference aggregation.

The purpose of this research is to characterise the internal conversations of individual young people in transition from state care, with a goal of supporting practitioners’ approaches to ‘pathway planning’, and contributing to theories of agency in emerging adulthood under conditions of long-term adversity. We used Margaret Archer’s theory of agency, in which internal conversations are regarded as playing a central role in mediating between structure and agency. Archer describes three different modes of (actively agential) internal conversation: communicative reflexivity, autonomous reflexivity and meta-reflexivity; and one mode of passive agency: fractured reflexivity – associated with adverse contextual constraints. In a qualitative design, using Archer’s open-ended interview framework we met nine participants, aged 19–24, varying considerably in outcome, recruited at a specialised service for care leavers in London UK. Analysis of the interview data included an extended phase of individual case analysis. Two participants experienced emerging active agency (however, both experienced elements of fractured reflexivity). Three participants experienced fractured reflexivity, with limited internal conversation, and low planning agency (however, each experienced green shoots of focused internal dialogue). Four participants experienced a survival-oriented mode of internal conversations, a category not found in Archer’s previous work. All four of these participants showed some elements of fractured reflexivity, but narrated rich internal conversations, including accounts of adverse experiences in which self-reliance was seen as having been essential. The majority of participants (across modes) found the idea of planning (beyond day-to-day) anathema.

This special issue of Social Choice and Welfare collects papers that study the interplay between deliberative and aggregative approaches to the formation of collective attitudes. Most of the contributions in this issue focus on so-called aggregative collective attitudes and, in particular, on aggregated beliefs, judgments, and preferences. As their name suggests, this type of collective attitude is defined through the mechanism that leads to its formation: aggregative collective attitudes are those that are obtained by putting together, i.e. aggregating, the attitudes of individuals. Beliefs, judgments, or preferences obtained through some form of voting are paradigm examples of aggregative attitudes. The properties of aggregative collective attitudes and their corresponding aggregation procedures are well studied. Social Choice Theory (Gaertner 2009) has mapped the possibilities and also the limits of the aggregation of preferences. The theory of Judgment Aggregation (Grossi and Pigozzi 2014) has done the same for the aggregation of categorical, logically connected judgments. Aggregative attitudes can be distinguished from common and from corporate ones (List 2014). Common collective attitudes are those that all group members share, and perhaps that are even public in the relevant sense (Williams 2023). Notions like common knowledge and common beliefs, central to theories of collective agency (Chant 2008) and epistemic game theory (Pacuit and Roy 2017), for instance, are probably the most well-known examples of common group attitudes. Corporate collective attitudes, on the other hand, are those that can be attributed to institutional or corporate agents based on their behavior or status (Tollefsen 2002; List and Pettit 2011) . The main difference between these three types of group attitudes is how they relate to the attitudes of the individual members. Common attitudes have the most direct relation: by definition, they are consensual and public. If a proposition is commonly believed, for instance, then every group member believes that proposition, believes that every group member believes it, and so on. This is not necessarily the case for aggregative or corporate attitudes. Voting, for instance, is typically viewed as a mechanism to aggregate diverging opinions. It is not meant to reflect an underlying consensus B Olivier Roy