People sometimes think in terms of ‘we’ referring to a group they belong to. When making decisions, they frame the decision problem as: ‘What should we do?’ instead of ‘What should I do?’. We study one particular approach to such ‘we-reasoning’, economist Michael Bacharach's theory of ‘team reasoning’, and relate it to philosopher Raimo Tuomela's distinction between ‘I-mode’ reasoning and ‘we-mode’ reasoning. We argue that these theories complement each other: Tuomela's philosophical theory provides a conceptual framework augmenting Bacharach's theory, and Bacharach's mathematical results support Tuomela's view on the irreducibility of the we-mode to the I-mode. We-mode reasoning can explain some kinds of human cooperative behaviour left unexplained by standard game theory. Standard game theory is not well-equipped to deal with we-mode reasoning but it can be extended by the methods developed by Bacharach. However, we argue that both standard game theory and Bacharach's theory require more attention to the information-sharing stages that precede actual decision making, and we describe a stage-based model of we-reasoning.
The Conceptual Framework of Game Theory and Presentation of Some Simple Games