 The term, “social institution” is somewhat unclear both in ordinary language and in the philosophical literature (see below). However, contemporary sociology is somewhat more consistent in its use of the term. Typically, contemporary sociologists use the term to refer to complex social forms that reproduce themselves such as governments, the family, human languages, universities, hospitals, business corporations, and legal systems. A typical definition is that proffered by Jonathan Turner (1997: 6): “a complex of positions, roles, norms and values lodged in particular types of social structures and organising relatively stable patterns of human activity with respect to fundamental problems in producing life-sustaining resources, in reproducing individuals, and in sustaining viable societal structures within a given environment.” Again, Anthony Giddens (1984: 24) says: “Institutions by definition are the more enduring features of social life.” He (Giddens 1984: 31) goes on to list as institutional orders, modes of discourse, political institutions, economic institutions and legal institutions. The contemporary philosopher of social science, Rom Harre follows the theoretical sociologists in offering this kind of definition (Harre 1979: 98): “An institution was defined as an interlocking double-structure of persons-as-role-holders or office-bearers and the like, and of social practices involving both expressive and practical aims and outcomes.” He gives as examples (Harre 1979: 97) schools, shops, post offices, police forces, asylums and the British monarchy. In this entry the above-noted contemporary sociological usage will be followed. Doing so has the virtue of grounding philosophical theory in the most salient empirical discipline, namely, sociology.