Ideology has been one of the most-contested issues in academic and political debate. The considerable amount of interest revealed for ideology has naturally paved the way for the emergence of a variety of approaches and theories related to ideology.
The origins of the term are nevertheless clear. The word “ideology” was coined during the French Revolution by Antoine Destutt de Tracy (1754 – 1836), and was first used in public in 1796. For de Tracy, idéologie referred to a new ‘science of ideas’, literally an idea-ology. With a rationalist zeal typical of the Enlightenment, he believed that it was possible objectively to uncover the origins of ideas, and proclaimed that this new science would come to enjoy the same status as established sciences such as biology and zoology
It can be asserted that ideology brings about two kinds of synthesis: between understanding and commitment, and between action and thought. In relation to the first synthesis, the fusion of understanding and commitment, ideology blurs the distinction between what ‘is’ and what ‘should be’. Ideologies are descriptive in that, in effect, they provide individuals and groups with an intellectual map of how their society works and more broadly with a general view of the world. Such descriptive understanding is deeply embedded within a set of normative or prescriptive beliefs, both about the adequacy of present social arrangements and about the nature of any alternative or future society. 
The second synthesis, the fusion of thought and action, is no less significant. On the one hand, ideologies resemble political philosophies in the sense that that they deal with abstract ideas and theories. On the other hand, some ideologies like fascism have always emphasized operative goals being action-orientated.
The term ideology can be defined in a number of ways. First of all, ideology is a sociological phenomenon. It reveals motives for one’s life and also for endangering one’s life. Ideologies are merciless if they are threatened by a counter-ideology. Ideologies are also seen as authority-orientated.
In addition, ideology is a historical phenomenon; it cannot come into being with the lack of a model of general ethical and cognitive principles that precedes itself. As a historical phenomenon, ideology takes place in particular socio-cultural legacies and social consciousness. Briefly, it can be stated that, ideology arises favoring a certain idea and/or belief or it arises opposing a certain idea and/or belief. Besides, ideology denotes some kind of collective belonging too. Moreover, ideology is a cultural phenomenon. It establishes specific relations among general cultural values, symbols and ideas. Also, ideology is a psychological phenomenon. The social life is complicated and too complex for many individuals to understand or make sense of. In this context, ideologies serve as a tool for individuals to help them make sense of social dynamics and specific social conditions. 
Related to ideology, Louis Althusser is one of the most important thinkers who have attracted a considerable amount of attention in recent years. According to Althusser, ideology with the political and economic levels constitutes the social formation. He argues that the formation of an ideology needs inevitably a political organization. He furthermore states that no social group can have a supreme authority without the ideological apparatuses of the state. What is meant by the term “ideological apparatuses of the state” consists of cultural and educational institutions like schools, media and so on.
Since the time of the French Revolution, ideological opinions have been classified most often in terms of a single left-right dimension. This usage derives from the fact that late-eighteenth century supporters of the status quo sat on the right side of the French Assembly hall and its opponents sat on the left. In the United States and elsewhere, it is becoming increasingly common to substitute “liberal” and “conservative” for “left” and “right,” respectively, and this equation expresses well the long-lasting ideological divide concerning preferences for change versus stability, which goes back at least as far as 1789.
On the other hand, different scholars attach different roles and functions to ideology. For instance, Marx sees ideology as the tool of the ruling class used in order to oppress the ruled people. Moreover, L. Althusser also sees ideology as a state apparatus employed for not losing political power and state authority. Another Marxist scholar Antonio Gramsci argues that ideological hegemony of the capitalist system plays a key role in political and social affairs.
In a world of competing truths, values and theories, ideologies seek to prioritize certain values over others, and to invest legitimacy in particular theories or sets of meanings. Furthermore, as ideologies provide intellectual maps of the social world, they help to establish the relationship between individuals and groups on the one hand, and the larger structure of power on the other.
The role and functions of ideologies can be listed as follows:
- To produce the values, symbols and ideas which are dominant in social life.
- To create a set of ideas belonging to a specific class.
- To legitimize a dominant political authority with adequate ideas.
- To legitimize a dominant political authority with inadequate ideas.
- To shape social interests.
- To give meaning to life.
- To produce a systematically- deviated communication.
- To create some sort of identicalness view.
- To direct the masses.
- To soften or pioneer tensions at the time of the contradictions seen between discourse and political power.
On the other hand, it could be asserted that, the formation of ideologies has also been largely determined by the socio-economic and cultural context of the geography it emerges. The social as well as economic unhappiness, the paradox witnessed between discourse and action, perceived feelings of absence and worry towards sudden changes or transformation all are influential in the production of ideologies.
Key elements which also shape the formation of ideologies are the issues which they centralize:
- The causes of the discomfort that is felt or perceived.
- The size of discomfort.
- The purposes of the behaviors that are drawn by the society as a whole.
- The general characteristics of the dominant value system and its perceived problems.
- Compared to given social systems, the obvious properties those are seen in other social systems.
In today’s world politics, there are different views about ideologies. As known, some people argue that in the post-Cold War era the dominance of US ideology has been proved. “The End of History” thesis of Francis Fukuyama is meaningful in justifying this argument. According to Fukuyama, the end of the Cold War stressed the triumph of capitalism against Soviet ideology – communism. In this era, the liberal values and free market economy cover world politics according to this view.
Apart from that, there is also a belief that in a globalizing world wherein the differences among the actors (states and non-state units) are getting minimized day by day, the function of ideologies has been eroding. This view suggests that, globalization implies that world politics is not shaped by ideology-driven policies. By contrast pragmatic motives play a major role.
In the contemporary world, it has been widely accepted that conflicts among the international actors contrasting with the above-noted statement, take place in an ideological framework. Today, ideological warfare is existent unlike the front wars in the past. It seems like the dominance of the term “ideology” will continue to occupy scholar and political agenda.
 Andrew Heywood, Political Ideologies, 4. Edition, Palgrave Macmillan, 2007, p. 5.
 D. McLellan, Ideology, Second Edition, Open University Press, 1995, p. 23.
 M. Seliger, Politics and Ideology, Free Press,1976, p. 47.
 Quoted in D. Ergil, İdeoloji: “Milliyetçilik, Muhafazakarlık, Halkçılık”, Sevinç Matbaası, Ankara, 1986, p.19-23.
 L. Althusser, “Ideology and Ideological State Apparatus”,in Lenin and Philosophy and Other Essays, 1971, Monthly Review Press, p. 9.
 Mümtaz’er Türköne (ed), Siyaset, Opus Yayınları, İstanbul, 11. Ed. 2010, p. 106.
 D. Ergil, ibid, p. 41.