La question que nous allons aborder dans ce cours est la suivante : peut-on réduire une société une simple agrégation d’individus, ou est-elle plus que cela ? Cette question introduit le débat qui oppose, en sciences sociales, les tenants de l’individualisme à ceux du holisme. En première approximation, les individualistes sociaux pensent qu’une société n’est rien de plus qu’une somme ou une agrégation d’individus. Les holistes sociaux pensent au contraire qu’une société n’est pas réductible à une simple agrégation d’individus. C’est (...) là une question fondamentale aussi bien pour les sociologues que pour les philosophes. Mais en tant que futurs ingénieurs, vous vous dites peut-être que cela ne va pas vous empêcher de dormir. Pour vous convaincre qu’il y a là certaines raisons sinon de faire des nuits blanches, du moins d’avoir quelques discussions animées, nous allons rapprocher cette question, que l’on traitera dans la première partie du cours, de deux autres dont l’enjeu vous semblera certainement plus immédiat. Nous les traiterons respectivement dans les deuxième et troisième parties du cours. (shrink)

The meaning of an utterance is often enriched by the pragmatic context in which it is uttered. This is because in ordinary conversations we routinely and uncontroversially compress what we say, safe in the knowledge that those interpreting us will ‘add in’ the content we intend to communicate. Does the same thing hold true in the case of legal utterances like ‘This constitution protects the personal rights of the citizen’ or ‘the parliament shall have the power to lay and collect (...) taxes’? This article addresses this question from the perspective of the constitutional originalist—the person who holds that the meaning of a constitutional text is fixed at some historical moment. In doing so, it advances four theses. First, it argues that every originalist theory is committed to some degree of pragmatic enrichment, the debate is about how much. Second, that in determining which content gets ‘added in’, originalists typically hold to a common knowledge standard for enrichment, protestations... (shrink)

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 disambiguation.

A recurring issue in any formal model representing agents' (changing) informational attitudes is how to account for the fact that the agents are limited in their access to the available inference steps, possible observations and available messages. This may be because the agents are not logically omniscient and so do not have unlimited reasoning ability. But it can also be because the agents are following a predefined protocol that explicitly limits statements available for observation and/or communication. Within the broad literature (...) on epistemic logic, there are a variety of accounts that make precise a notion of an agent's "limited access" (for example, Awareness Logics, Justification Logics, and Inference Logics). This paper interprets the agents' access set of formulas as a constraint on the agents' information gathering process limiting which formulas can be observed. (shrink)

Famously, Kripke has argued that the central portion of the Philosophical Investigations describes both a skeptical paradox and its skeptical solution. Solving the paradox involves the element of the community, which determines correctness conditions for rule-following behavior. What do such conditions precisely consist of? Is it accurate to say that there is no fact to the matter of rule following? How are the correctness conditions sustained in the community? My answers to these questions revolve around the idea that a rule (...) is followed insofar as a convention is in place. In particular, I consider the game-theoretic definition of convention offered by David Lewis and I show that it illuminates essential aspects of the communitarian understanding of rule-following. Make the following experiment: say “It’s cold here” and mean “It’s warm here”. Can you do it?Ludwig Wittgenstein, Philosophical Investigations, 1953, §510.I can’t say “it’s cold here” and mean “it’s warm here”—at least, not without a little help from my friends.David Lewis, Convention. (shrink)

This dissertation is a contribution to the philosophy of language. Its central question is: In virtue of which facts do linguistic expressions mean what they do? E.g. why does “apple” mean apple in English? The question receives a systematic answer; in short: Linguistic expressions mean what they do because among their users, there are linguistic conventions and social norms to use and understand them in certain ways. The answer is clarified and defended as a central thesis. For in this form, (...) it is at best a slogan: What is meaning? What is it to use and understand expressions? What are conventions and social norms anyway? How does the use and understanding determine meaning? The goal of the dissertation consists in answering these questions. (shrink)

The combination of logic and game theory provides a fine-grained perspective on information and interaction dynamics, a Theory of Play. In this paper we lay down the main components of such a theory, drawing on recent advances in the logical dynamics of actions, preferences, and information. We then show how this fine-grained perspective has already shed new light on the long-term dynamics of information exchange, as well as on the much-discussed question of extensive game rationality.

Decision-making typically requires judgments about causal relations: we need to know the causal effects of our actions and the causal relevance of various environmental factors. We investigate how several individuals' causal judgments can be aggregated into collective causal judgments. First, we consider the aggregation of causal judgments via the aggregation of probabilistic judgments, and identify the limitations of this approach. We then explore the possibility of aggregating causal judgments independently of probabilistic ones. Formally, we introduce the problem of causal-network aggregation. (...) Finally, we revisit the aggregation of probabilistic judgments when this is constrained by prior aggregation of qualitative causal judgments. (shrink)

This paper investigates the epistemic assumptions that David Lewis makes in his account of social conventions. In particular, I focus on the assumption that the agents have common knowledge of the convention to which they are parties. While evolutionary analyses show that the common knowledge assumption is unnecessary in certain classes of games, Lewis’ original account (and, more recently, Cubitt and Sugden’s reconstruction) stresses the importance of including it in the definition of convention. I discuss arguments pro et contra to (...) argue that, although the assumption might be relevant to a descriptively adequate account of social convention, it is not required for its rational reconstruction. I then point out that Lewis’ account, properly speaking, is of common reason to believe, rather than of common knowledge, and argue that, in order to formalize aptly the distinction between reason to believe and belief, standard formal epistemic models need to be supplemented with so-called awareness structures. Finally, I stress that the notion of knowledge implicit in Lewis’ text involves interesting elements that cannot be captured in the standard propositional formalizations, but need the full expressive force of quantified epistemic logic. (shrink)

This article will compare and contrast two very different accounts of convention: the game-theoretical account of Lewis in Convention, and the account initially proposed by Margaret Gilbert (the present author) in chapter six of On Social Facts, and further elaborated here. Gilbert’s account is not a variant of Lewis’s. It was arrived at in part as the result of a detailed critique of Lewis’s account in relation to a central everyday concept of a social convention. An account of convention need (...) not be judged by that standard. Perhaps it reveals the nature of an important phenomenon. Looked at in that light, these very different accounts are not incompatible. Indeed, neither should be ignored if one is seeking to understand the way in which human beings arrive at some degree of social order. (shrink)

In this paper it is shown how a formal theory of interpretation in Montague’s style can be reconciled with a view on meaning as a social construct. We sketch a formal theory in which agents can have their own theory of interpretation and in which groups can have common theories of interpretation. Frege solved the problem how different persons can have access to the same proposition by placing the proposition in a Platonic realm, independent from all language users but accessible (...) to all of them. Here we explore the alternative of letting meaning be socially constructed. The meaning of a sentence is accessible to each member of a linguistic community because the way the sentence is to be interpreted is common knowledge among the members of that community. Misunderstandings can arise when the semantic knowledge of two or more individuals is not completely in sync. (shrink)

Common knowledge is ubiquitous in our lives and yet there remains considerable uncertainty about how to model or understand it. Standard analyses of common knowledge end up being challenged by either regress or circularity which then give rise to well-known paradoxes of practical reasoning, such as the Two Generals’ Paradox. This paper argues that the nature and utility of common knowledge can be illuminated by appeal to Wittgenstein’s Hinge Epistemology. It is argued that those things that we standardly think of (...) as being common knowledge in our lives are the same as those that Wittgenstein identified as hinge certainties. This identification of common knowledge with hinge certainties allows us to resolve the regress problem for common knowledge and explain how the Two Generals’ Paradox arises. (shrink)

Some arguments against the assumption that ordinary people may share common knowledge are sound. The apparent cost of such arguments is the rejection of scientific theories that appeal to common knowledge. My proposal is to accept the arguments without rejecting the theories. On my proposal, common knowledge is shared by ideally rational people, who are not just mathematically simple versions of ordinary people. They are qualitatively different from us, and theorizing about them does not lead to predictions about our behavior. (...) Nevertheless, models of action that assume common knowledge have a role to play in our understanding of collective rationality. (shrink)

This article describes how the facts in social reality take an intermediate position between objective facts and purely subjective ‘facts’. In turn, these social facts can be subdivided into constructivist and non-constructivist facts. The defining difference is that non-constructivist facts are completely determined by an approximate consensus between the members of a social group, while constructivist facts are founded in such a consensus but can nevertheless be questioned. Ought fact are such constructivist facts. Because they are founded in social reality, (...) a naturalistic theory of ought facts is attractive. Because constructivist facts are always open to questioning, we can explain why the facts in social reality may found ought facts but are nevertheless not the final word about them. (shrink)

Within analytic philosophy, the existence of collective knowledge has been motivated by means of two apparently distinct, and in direct competition with one another, theoretical approaches: (i) the commitment model and (ii) the distributed model. This paper agues, however, that to fully account for collaborative knowledge—i.e., a special kind of collective knowledge—both models are required. In other words, there is at least one kind of collective knowledge, the account of which requires treating the two models not as competitors but as (...) complementary to each other. If that’s correct, not only can we gain a deeper understanding of the specifics surrounding collaborative knowledge but also a clearer picture of the broader debate surrounding collective knowledge. (shrink)

This book offers a state-of-the-art introduction to the basic techniques and results of neighborhood semantics for modal logic. In addition to presenting the relevant technical background, it highlights both the pitfalls and potential uses of neighborhood models – an interesting class of mathematical structures that were originally introduced to provide a semantics for weak systems of modal logic. In addition, the book discusses a broad range of topics, including standard modal logic results ; bisimulations for neighborhood models and other model-theoretic (...) constructions; comparisons with other semantics for modal logic ; neighborhood semantics for first-order modal logic, applications in game theory ; applications in epistemic logic ; and non-normal modal logics with dynamic modalities. The book can be used as the primary text for seminars on philosophical logic focused on non-normal modal logics; as a supplemental text for courses on modal logic, logic in AI, or philosophical logic ; or as the primary source for researchers interested in learning about the uses of neighborhood semantics in philosophical logic and game theory. (shrink)

A link between populism and social media is often suspected. This paper spells out a set of possible mechanisms underpinning this link: that social media changes the communication structure of the public sphere, making it harder for citizens to obtain evidence that refutes populist assumptions. By developing a model of the public sphere, four core functions of the public sphere are identified: exposing citizens to diverse information, promoting equality of deliberative opportunity, creating deliberative transparency, and producing common knowledge. A wellworking (...) public sphere allows citizens to learn that there are genuine disagreements among citizens that are held in good faith. Social media makes it harder to gain this insight, opening the door for populist ideology. (shrink)

Salience reasoning, many have argued, can help solve coordination problems, but only if such reasoning is supplemented by higher-order predictions, e.g. beliefs about what others believe yet others will choose. In this paper, I will argue that this line of reasoning is self-undermining. Higher-order behavioral predictions defeat salience-based behavioral predictions. To anchor my argument in the philosophical literature, I will develop it in response and opposition to the popular Lewisian model of salience reasoning in coordination games. This model imports the (...) problematic higher-order beliefs by way of a ‘symmetric reasoning’ constraint. In the second part of this paper, I will argue that a player may employ salience reasoning only if she suspends judgment about what others believe yet others will do. (shrink)

There are several ways to quantify over public announcements. The most notable are reflected in arbitrary, group, and coalition announcement logics, with the latter being the least studied so far. In the present work, we consider coalition announcements through the lens of group announcements, and provide a complete axiomatisation of a logic with coalition announcements. To achieve this, we employ a generalisation of group announcements. Moreover, we study some logical properties of both coalition and group announcements that have not been (...) studied before. (shrink)

When you and I share an experience, each of us lives through a we-experience. The paper claims that we-experiences have unique phenomenality and structure. First, we-experiences’ phenomenality is characterised by the fact that they feel like ours to their subject. This specific phenomenality is contended to derive from the way these experiences self-represent: a we-experience exemplifies us-ness or togetherness because it self-represents as mine qua ours. Second, living through a we-experience together with somebody else is not to have this experience (...) in parallel with the experience of the other. Rather, the paper argues that a we-experience is partly co-constituted by the experience of the other. After offering an account of the phenomenality and constitution of we-experiences, which traces these two elements back to the subject’s self-understanding as a group member, the paper argues for the claim that an experience’s for-us-ness is committal to this experience being co-constituted by another we-experience. (shrink)

En este ensayo exploramos una perspectiva epistemológica en la que el elemento social y colectivo del conocimiento juega un papel fundamental en la explicación de su producción y transmisión. Primero presentamos y criticamos una posición individualista que ha sido dominante en la epistemología contemporánea y cuyas raíces pueden trazarse, al menos, hasta Descartes. Posteriormente introducimos y defendemos nuestra propia mirada, una en la que el conocimiento es un proceso constituido por un conjunto de actividades y prácticas que tiene un carácter (...) material. (shrink)

We study shared intentions in what we call “loose groups”. These are groups that lack a codified organizational structure, and where the communication channels between group members are either unreliable or not completely open. We start by formulating two desiderata for shared intentions in such groups. We then argue that no existing account meets these two desiderata, because they assume either too strong or too weak an epistemic condition, that is, a condition on what the group members know and believe (...) about what the others intend, know, and believe. We propose an alternative, pooled knowledge, and argue that it allows formulating conditions on shared intentions that meet the two desiderata. (shrink)

An opinionated introduction to philosophical issues connected to common knowledge.

En este ensayo exploramos una perspectiva epistemológica en la que el elemento social y colectivo del conocimiento juega un papel fundamental en la explicación de su producción y transmisión. Primero presentamos y criticamos una posición individualista que ha sido dominante en la epistemología contemporánea y cuyas raíces pueden trazarse, al menos, hasta Descartes. Posteriormente introducimos y defendemos nuestra propia mirada, una en la que el conocimiento es un proceso constituido por un conjunto de actividades y prácticas que tiene un carácter (...) material. (shrink)

There are modes of presentation of a person in thought corresponding to the first and third person pronouns. This paper proposes that there is also thought involving a second person mode of presentation of another, which might be expressed by an utterance involving ‘you’, but need not be expressed linguistically. It suggests that co-operative activity is the locus for such thought. First person thought is distinctive in how it supplies reasons for the subject to act. In co-operative action there is (...) first person plural intending and judging. So there is a way of thinking of another, when openly co-operating with him or her, which plays the distinctive role of giving reason for contribution to the co-operative activity. In slogan form, ‘you’ is ‘we minus I’. The way children learn to use second and third person pronouns is naturally explained on this view. Contrasting less sophisticated kinds of co-operative activity with more sophisticated forms, and considering some issues about common knowledge and commo.. (shrink)

This paper presents the results of an experiment on mutual versus common knowledge of advice in a two-player weak-link game with random matching. Our experimental subjects play in pairs for thirteen rounds. After a brief learning phase common to all treatments, we vary the knowledge levels associated with external advice given in the form of a suggestion to pick the strategy supporting the payoff-dominant equilibrium. Our results are somewhat surprising and can be summarized as follows: in all our treatments both (...) the choice of the efficiency-inducing action and the percentage of efficient equilibrium play are higher with respect to the control treatment, revealing that even a condition as weak as mutual knowledge of level 1 is sufficient to significantly increase the salience of the efficient equilibrium with respect to the absence of advice. Furthermore, and contrary to our hypothesis, mutual knowledge of level 2 induces, under suitable conditions, successful coordination more frequently than common knowledge. (shrink)

The first hurdle to overcome in approaching the complex topic of the relation between language and consciousness is terminology. So let me begin, in good philosophical style, by explaining the senses in which I use the three lexical terms in the title. Luckily I need not explain those of the three grammatical words the, of, and on: there is probably a minor library of semantic literature devoted to that. I need not, since I both know their meanings pre-theoretically, and know (...) that my readers, as users of English, know them. The significance of this simple fact concerning the meaning of all everyday words, in everyday constructs, is something that I will return to, since it plays a central role in the argument in Section 2. However, with abstract, theoretically loaded nominalizations such as dependence, language, and most of all consciousness, we need to beware since we cannot assume common knowledge -- myriads of misunderstandings arise since we mean somewhat different 'things' by them. I start with the easiest, by which I mean specifically ' dependence of language on consciousness', explaining only afterward what I mean by the latter terms. I ask the reader to bear this circularity with me. (shrink)