In this paper it is argued that a) altruism is an inadequate label for human cooperative behavior, and b) an adequate account of cooperation has to depart from the standard economic model of human behavior by taking note of the agents' capacity to see themselves and act as team-members. Contrary to what Fehr et al. seem to think, the main problem of the conceptual limitations of the standard model is not so much the assumption of sel shness but rather the (...) atomistic conception of the individual. A much-neglected question of the theory of cooperation is how the agent's social identity is determined, i.e. how individuals come to think of themselves and act as members of a group. Considering as an example one of Fehr et al.'s third party punishment experiments, I shall argue that the agents' identities are strongly in uenced by the way the experiment is presented to the participants, especially by the collectivity-related vocabulary used in the instructions. (shrink)