Cedric Paternotte

We consider the question: under what circumstances can the concept of adaptation be applied to groups, rather than individuals? Gardner and Grafen (2009, J. Evol. Biol.22: 659–671) develop a novel approach to this question, building on Grafen's ‘formal Darwinism’ project, which defines adaptation in terms of links between evolutionary dynamics and optimization. They conclude that only clonal groups, and to a lesser extent groups in which reproductive competition is repressed, can be considered as adaptive units. We re-examine the conditions under which the selection–optimization links hold at the group level. We focus on an important distinction between two ways of understanding the links, which have different implications regarding group adaptationism. We show how the formal Darwinism approach can be reconciled with G.C. Williams’ famous analysis of group adaptation, and we consider the relationships between group adaptation, the Price equation approach to multi-level selection, and the alternative approach based on contextual analysis.

La plupart des nombreuses définitions existantes d’une action coopérative en fournissent des conditions suffisantes plutôt que nécessaires. Nous définissons ici une forme minimale de coopération, correspondant aux actions de masse, telles des manifestations. Nous en détaillons les aspects intentionnel, épistémique, stratégique et téléologique, généralement obtenus par affaiblissement spécifique de concepts classiques. Parallèlement, nous soulignons le rôle crucial de concepts issus de la théorie des jeux pour la définition d’une action coopérative. Enfin, nous soutenons que la rationalité d’une action coopérative minimale est cruciale à sa réalisation et pas seulement possible ou souhaitable comme le soutiennent les analyses habituelles.

Over the last three decades, joint action has received various definitions, which for all their differences share many features. However, they cannot fit some perplexing cases of weak joint action, such as demonstrations, where agents rely on distinct epistemic sources, and as a result, have no first-hand knowledge about each other. I argue that one major reason why the definition of such collective actions is akin to the classical ones is that it crucially relies on the concept of common knowledge. To this end, I first argue for the necessity of common knowledge for joint action in general due to the increased reliability of success it entails. I then defend the relevance of common knowledge against several criticisms, point at an adequate weakening, and discuss alternative approaches. Although structurally weaker, the common knowledge has a richer content in weak joint actions. As a result, even if the links between individuals are seriously stretched, much is still shared among them. Weak joint actions still require considerable cognitive abilities indeed

There exist many definitions of human joint action, or of what makes a group similar to an individual. However, they do not agree and are not directly reducible to each other. This multiplicity is due to a lack of constraints on them. I argue that they should at least meet an efficiency constraint: any account of joint action has to justify how it reliably leads agents to cooperation. One avenue consists in exploring the analogy between definitions of joint action and of biological individuality. The main components for biological individuality have been identified and their relations are much better understood than those between the components of human joint action. I show that there are surprisingly strong analogies between the criteria and mechanisms for joint action and for biological individuality. As a result, we can import some insights of the biological literature to define what a joint action is, and when a group can and should be considered as an individual.

Most definitions of cooperation provide sufficient but not necessary conditions. This paper describes a form of minimal cooperation, corresponding to mass actions implying many agents, such as demonstrations. It characterizes its intentional, epistemic, strategic, and teleological aspects, mostly obtained from weakening classical concepts. The rationality of minimal cooperation turns out to be part of its definition, whereas it is usually considered as an optional though desirable feature. Game-theoretic concepts thus play an important role in its definition. The paper concludes by answering concrete questions about what should and should not be called cooperation

There has been a significant interest in the recent literature in developing a solution to the problem of theory choice which is both normative and descriptive, but agent-based rather than rule-based, originating from Pierre Duhem’s notion of ‘good sense’. In this paper we present the properties Duhem attributes to good sense in different contexts, before examining its current reconstructions advanced in the literature and their limitations. We propose an alternative account of good sense, seen as promoting social consensus in science, and show that it is superior to its rivals in two respects: it is more faithful to Duhemian good sense, and it cashes out the effect that virtues have on scientific progress. We then defend the social consensus account against objections that highlight the positive role of diversity and division of labour in science

Defined and formalized several decades ago, widely used in philosophy and game theory, the concept of common knowledge is still considered as problematic, although not always for the right reasons. I suggest that the epistemic status of a group of human agents in a state of common knowledge has not been thoroughly analyzed. In particular, every existing account of common knowledge, whether formal or not, is either too strong to fit cognitively limited individuals, or too weak to adequately describe their state. I provide a realistic definition of common knowledge, based on a formalization of David Lewis’ seminal account and show that it is formally equivalent to probabilistic common belief. This leads to a philosophical analysis of common knowledge which answers several common criticisms and sheds light on its nature.

Robustness analysis is widespread in science, but philosophers have struggled to justify its confirmatory power. We provide a positive account of robustness by analysing some explicit and implicit uses of within and across-model robustness in evolutionary theory. We argue that appeals to robustness are usually difficult to justify because they aim to increase the likeliness that a phenomenon obtains. However, we show that robust results are necessary for explanations of phenomena with specific properties. Across-model robustness is necessary for how-possibly explanations of multiply instantiated phenomena, while within-model robustness is necessary for explanations of phenomena with multiple evolutionary starting points. In such cases, the appeal of robustness is explanatory rather than confirmatory.

We critically examine a number of aspects of Grafen’s ‘formal Darwinism’ project. We argue that Grafen’s ‘selection-optimality’ links do not quite succeed in vindicating the working assumption made by behavioural ecologists and others—that selection will lead organisms to exhibit adaptive behaviour—since these links hold true even in the presence of strong genetic and developmental constraints. However we suggest that the selection-optimality links can profitably be viewed as constituting an axiomatic theory of fitness. Finally, we compare Grafen’s project with Fisher’s ‘fundamental theorem of natural selection’, and we speculate about whether Grafen’s results can be extended to a game-theoretic setting