This dissertation gives a philosophical account of acting together with others in the sense of collaboration or partnership. One part of that project is empirical. I report and elaborate on experimental research conducted on our everyday notion of acting together in order to better understand what it is. Another part, which offers a philosophical theory of how we do it, defends the “higher-order interdependence view” of collective intention. I argue that, compared to other kinds of existing views, this theory provides the best explanation of the results of the empirical research.
