Abstract Orthodox decision theory presupposes that agency is invested in individuals. An opposing literature allows team agency to be invested in teams whose members use distinctive modes of team reasoning. This paper offers a new conceptual framework, inspired by David Lewis's analysis of common reasons for belief, within which team reasoning can be represented. It shows how individuals can independently endorse a principle of team reasoning which prescribes acting as a team member conditional on assurance that others have endorsed the (...) same principle. It argues that there can be such assurance even when no individual has an obligation to act on team reasoning. *This paper originated in a lecture that I gave at a Colloquium on Collective Intentions at Erasmus University Rotterdam. I thank participants, and particularly Govert den Hartogh, for comments. The analysis presented in this paper is an offshoot of a larger project, which uses David Lewis's work as the starting point for a reconstruction of the foundations of game theory. That project is joint work with Robin Cubitt. The specific idea of using this approach to analyse team reasoning grew out of a discussion with Michael Bratman. My work was supported by the Leverhulme Trust. (shrink)

Humans and animals make inferences about the world under limited time and knowledge. In contrast, many models of rational inference treat the mind as a Laplacean Demon, equipped with unlimited time, knowledge, and computational might. Following H. Simon's notion of satisficing, the authors have proposed a family of algorithms based on a simple psychological mechanism: one-reason decision making. These fast and frugal algorithms violate fundamental tenets of classical rationality: They neither look up nor integrate all information. By computer simulation, the (...) authors held a competition between the satisficing "Take The Best" algorithm and various "rational" inference procedures. The Take The Best algorithm matched or outperformed all competitors in inferential speed and accuracy. This result is an existence proof that cognitive mechanisms capable of successful performance in the real world do not need to satisfy the classical norms of rational inference. (shrink)