Human lives involve remarkable forms of social organization. Not only do they work together towards common goals, but they also divide themselves into mutually exclusive, and sometimes opposing, groups. A comprehensive theory of social phenomena should help us understand and appreciate the complexity and diversity of the social world. Towards building a comprehensive theory of social phenomena, this thesis argues that the key to a theory’s success lies in an in-depth investigation of two closely connected but ultimately separable concepts: “reasons” and “norms.” This thesis attempts to show that our social world can be satisfactorily explained in terms of “motivating reasons” and “norms,” neither of which requires any prior understanding of the nature of human collectivity. In contrast, collectivists, such as Margaret Gilbert and John Searle, describe our social world in terms of collective, group-centric concepts such as joint commitment, shared intentionality and we-reasoning. Taking joint commitment as an example, this thesis defends the singularist approach against collectivism by developing a novel singularist framework, the MR-N (Motivating Reason-Norm) framework and show how the MR-N framework can be used fully describe any collective concept and, in particular, the concept of joint commitment. As a result, the diverse range of social phenomena that can be described using the concept of joint commitment can also be described in terms of the MR-N framework. This thesis then briefly considers a popular singularist theory proposed by Michael Bratman, who seeks to combine a theory of planning together with a theory of law proposed by H. L. A. Hart and compares Bratman’s singularist theory to the singularist MR-N framework.