Ideology is a controversial political term that has often carried pejorative implications. In the social-scientific sense, a political ideology is a more or less coherent set of ideas that provides a basis for organized political action. Its central features are an account of existing power relationships, a model of a desired future, and an outline of how political change can and should be brought about. Ideologies link political theory with political practice. On one level, ideologies resemble political philosophies, in that they constitute a collection of values, theories and doctrines; that is, a distinctive world-view. On another level, however, they take the form of broad political movements, and are articulated through the activities of political leaders, parties and groups Every ideology can be associated with a characteristic set of principles and ideas. Although these ideas 'hang together', in the sense that they interlock in distinctive ways, they are systematic or coherent only in a relative sense. All ideologies thus embody a range of rival traditions and internal tensions. Conflict within ideologies is thus sometimes more passionate than that between ideologies.