 The entry has five sections. In the first section an overview of various salient accounts of social institutions and their main points of theoretical difference is provided. Accounts emanating from sociological theory as well as philosophy are mentioned. Here, as elsewhere, the boundaries between philosophy and non-philosophical theorising in relation to an empirical science are vague. Hence, it is important to mention theories such as those of Emile Durkheim and Talcott Parsons, as well as those of John Searle and David Lewis. Moreover, it is also important to highlight some of the theoretical differences, notably those of an ontological character.