A comprehensive and coherent set of basic beliefs about political, economic, social and cultural affairs that is held in common by a sizable group of people within a society. Such interrelated ideas and teachings purport both to explain how political, economic, social and cultural institutions really do work and also to prescribe how such institutions ought ideally to operate. Conservative ideologies seek to demonstrate a close correspondence between "the way things are" and "the way things ought to be," thus legitimizing the existing order in the eyes of those who can be convinced to believe in the ideology. Radical and revolutionary ideologies, on the other hand, set unconventional, higher, or even utopian standards with regard to what would constitute a legitimate and supportable social-economic-political system and then demonstrate in detail that the existing order does not even come close to meeting these standards, thereby de-legitimizing the existing system and helping mobilize believers in the ideology for concerted action to reform or overthrow the existing order. (In addition to their descriptive and prescriptive functions about existing and ideal social orders, ideologies may also include more specialized doctrines regarding the most suitable political strategies and tactics to be pursued by believers in their efforts to shore up or undermine the existing order.)

One useful way of categorizing ideologies from a political point of view focusses on differences in the ideologies' prescriptions for how much the government ought to be involved in directing or regulating economic, social and cultural affairs and how much individuals or voluntary organizations ought to be left alone to make their own (widely varied) decisions in these spheres of life. In this course, for example, we frequently employ a two-dimensional classification of ideologies proposed by Maddox and Lilie that is based on assessing people's preferences for government regulation versus non-regulation in:

1. Economic decisions
2. Non-economic or life-style decisions.

It should be noted that the term "ideology" often has a somewhat derogatory flavor, especially in Anglo-American societies, because it often carries the implication that "ideological" thought is unduly biased, dogmatic and distorted, an obstacle rather than an aid in perceiving how the world "really" works. ("You, sir, are an ideologue. I, on the other hand, am a pragmatic man of reason who sees things the way they really are.")

[See also: anarchism, communism, conservatism, fascism, legitimacy, liberalism, libertarianism, populism, socialism, totalitarianism]