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For the accomplishment of an act, an actor is dependent of the work of other actors. When collaborating incommensurability (a fundamental not sharing of an understanding) between practices is a factor that has to be overcome for acts to be successful. Actors share terrains of incommensurability and terrains of commensurability. Project management, meta-cognitive skills, boundary objects and a shared perspective help in this. In communities of practice, taxonomies are built that represent conceptual schemes that define how actors act. In this context an act cannot be true or false. It is a result of the being-in the world that a taxonomy provides (Kuhn 2000). In the community that an actor operates in multiple mediated presences contribute to the evolving taxonomies, which influence and are a consequence of the way actors inter-act. Mediated presence contributes to the evolving taxonomies in communities in which witnessed presence plays a crucial role. I conclude that especially when vital information is generated mediated presence contributes significantly to the capacities that natural presence provides,