There is no one central theory used by CDA. There is a range and variety, and many authors use a technique of moving from theory to discourse, then back to theory :-

• Epistemology. Models of human perception in general, its limits, conditions and contingencies, and particularly scientific perception
• General Social Theories ('Grand Theories'). These try to conceptualise relations between social structure and social action, thus linking macro- and micro-sociological phenomena. Within this,
  some are more structuralist (often top-down explanations = structure -> action),
  others are more individualist (often bottom-up explanations = action -> structure)
  more modern theories imply that there is some kind of circularity between structure and action
• Middle range theories. These may focus on:-
  Specific social phenomena (conflict, cognition, social networks)
  Specific sub-systems of society (economy, politics, religion)
  Micro-sociological Theories. These try to explain social interaction, e.g. the double contingency problem (A and B have never met, how will they relate, what will they do if they meet), or the reconstruction of everyday procedures, whereby members of society create their own social order. ……. As such, it relates to ethno-methodology.
• Socio-psychological theories. These prefer causal explanations compared to micro-sociology, and concentrate on the social conditions of cognition and emotion
• Discourse Theories. Conceptualise discourse as a social phenomenon, and try to explain its genesis and structure
• Linguistic Theories. Explain the patterns specific to language systems and verbal communication - theories of argumentation, grammar, rhetoric, etc (based on Meyer, 2001, pp 19- 20 references)

All of the above theory types can be found in CDA, so at first it seems that what unifies CDA is the specifics of research questions rather than theoretical positioning.

An important point about CDA is that the range of theories possible in CDA helps it to claim that it is interdisciplinary, and by using methods based on several of these theory groups, a triangulation process can be carried out which helps to validate the results achieved.

Fairclough and Kress have stated that a full account of discourse would involve a theorisation and description of both the

1. social processes and structures which give rise to the production of a text,
2. and of the social structures and processes within which individuals or groups as social historical subjects, create meaning in their interaction with texts. (derived from Wodak, 2001, p. 3 references)

Clearly, to achieve a complete description of BOTH the circumstances surrounding the creating of a text AND the circumstances surrounding the reader/researcher is almost impossible to envisage. In addition to this, there is the challenge of carrying out a FULL analysis of a text. In the example of my text, I could exhaust the reader with a 1000 pages of full analysis of my 240-word text. To describe the circumstance of the creation of the text and my own circumstance as researcher would also be major works. At the other extreme, I could simply review it or make comments. This might entertain or influence, but would not ultimately have any validity. Inevitably, I am compromising by selecting the most interesting parts of the 'full analysis', giving some information of the circumstances, and hoping to avoid mere commentary.

Scollon also adds (mostly adapted by me) (pp. 139-141 references) :-

• Social problems in our contemporary world are inextricably linked to texts ….. Social problems are couched in public and private discourses that shape the definition of these problems as well as inhibiting social change.
  
• Our actions are frequently accompanied by language and, conversely, much of what we say is accompanied by action
• The programme of CDA is founded in the idea that the analysis of discourse opens a window on social problems because social problems are largely constituted in discourse
• Nevertheless, it remains problematical to this programme to establish the links between discourses and social actions
• Also, there is sometimes an almost unbridgeable gap between the discourse and the people whose social actions are involved, e.g. with HIV, the 'official' discourse is almost entirely disconnected from the drug users and others who suffer from HIV, or whose behaviour means they are likely to get infected

We have a picture of discourse that clearly affects social structures and systems, but the way that it does this cannot be directly ascertained, although CDA can make progress in becoming aware of the problems illustrated above, and so can help to resolve them

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