In this contribution I will pick out firstly the basic forms of cooperation and We-intentionality: language, social objects, documents, commitment, parcelling of tasks and recognition of a we-authority. Unfortunately, this list of generic social attitudes explains only various aspects of the social reality without explaining their emergence. Therefore, I will propose to treat We-Intentionality as the outcome of an irreducible belonging to a group, whereby the members develop cognitive capacities by participating in group activities and engaging in joint attention, and moreover, they learn language, symbols and documents as a form of shared intentionality. Finally I will introduce a novel theory of belonging as personal – and partially irreflexive – engagement for the preservation of one’s own group by means of cooperatively self-aware joint activities