The Introduction and first chapter of the Archeology focus largely on a contradicting received ideas about the continuity of history. Foucault argues that even the new study of the history of ideas, although it targets moments of transition between historical worldviews, is ultimately dependent on continuities that break down under closer inspection. The history of ideas marks points of discontinuity between broadly defined modes of knowledge, but the assumption that those modes exist as wholes fails to do justice to the complexities of discourse. Discourses emerge and transform not according to a developing series of unarticulated, common worldviews, but according to a vast and complex set of discursive and institutional relationships. These relationships are defined as much by breaks and ruptures as by unified themes; in fact, discontinuity is an integral component of unified discursive formations.
Discontinuities in discourse can take the form of internal contradictions, and here too Foucault takes the history of ideas to task for failing to examine its own assumptions. The history of ideas depends on a view of discursive contradictions as obstacles to be explained away in historical analysis. Paradoxically, however, it also takes contradiction as the deep, almost metaphysical principle on which discourse depends (without contradictions, what would there be to discuss?). Foucault sees both these notions of contradiction as violations of the attempt to describe discourses on their own terms. For him, contradiction is yet another general label for a set of widely divergent discursive processes. Foucault critiques not only assumed forms of historical continuity, but also assumptions that historical discontinuity is one (continuous) kind of thing.
Foucault's emphasis on discontinuities is also a function of his strict definition of what discourse is and his tireless insistence on describing that discourse in its clear, definable details, without any 'interpretation.' The archeological method aims to describe discourse only in its active existence in the world, and eschews any reading of it that seeks a psychology, a spirit, or anything else beyond the statement itself and its describable relations with other statements. This means that archeology must assume nothing about the hidden unities that secretly bind together the many things people say; any discursive unity must be described anew, on its own terms.
Foucault's version of discourse is the most pervasive theoretical idea in the Archeology. The term has a history as the object of study for a new kind of history, the history of ideas. But Foucault devotes much of the Archeology to refining and winnowing the usual sense of discourse into an object of analysis that is very strictly delimited. The first major alteration that Foucault makes is a casting aside of everything but the processes of discourse itself. Thus, his method studies only the set of 'things said' in their emergences and transformations, without any speculation about the overall, collective meaning of those statements. Archeology does not describe history through discourse; it describes the history of discourse.
Foucault carries his insistence on discourse-in-itself down to the most basic unit of things said: the statement. Just as discourse is never taken as a partial sign of a greater, partially hidden historical truth, so individual statements are never taken as expressions of a psychology, nor even as vehicles for referential meanings and propositions. Foucault addresses statements only in the specific conditions of their emergence and transformation; these conditions are themselves discursive (and sometimes institutional).
Thus, discourse is not just a set of articulated propositions, nor is it the trace of an otherwise hidden psychology, spirit, or encompassing historical idea; it is the set of relations within which all of these other factors gain their sense (their conditions of possibility). This argument is responsible both for the immense success of Foucault's method and for the most persistent criticisms of it. The idea that discourse can be described in and of itself, not as a sign of what is known but as a precondition for knowledge, opens up limitless possibilities for showing that what we think we know is actually contingent on how we talk about it.
One of the most important themes of the Archeology is Foucault's evolving description of what knowledge is. Since the archeological method sets aside any psychological notions and any assumptions of the rational progression of history, its take on knowledge is unique and quite radical. The history of ideas (and some of Foucault's earlier work as well) deals with the series of epistemes through which a given science has progressed; the term denotes a prevailing mode of knowledge and investigation. In the Archeology, Foucault carefully redefines the notion of the episteme. The term no longer refers to a set of things known by a collective scientific subject, but rather to a set of discursive relations without content and without a knowing subject.
The episteme, then, is that specific set of relations that makes it possible for discourse to be taken as 'knowledge' and then as 'science;' it mediates between less systematic discursive positivities and increasingly regularized ones. Knowledge itself, as far as Foucault's method is concerned, is just another discursive effect, albeit one of the most pervasive and important ones. Knowledge in a given historical period is not defined by propositions proved, nor even by things 'known' by an individual or collective someone (remember, no psychology). Knowledge becomes the unstable, complex set of discursive relations that make it possible for a statement to qualify as something that is 'known.' If the history of ideas was concerned with showing the transition between modes of knowledge, archeology is concerned with describing the transformation of the conditions that determine what counts as knowledge.
Other work of Foucault's explores these issues in a way that is more political and more personal. Foucault increasingly analyzes the conditions that define what counts as knowledge in terms of the way those conditions are bound up with systems of surveillance, discipline, and power. The question also becomes one of how we come to know ourselves and to be known (and labeled) as selves.
Foucault calls his new historical method an 'archeology' to designate a kind of impersonal, objective historical analysis that replaces the interpretation of history with a rigorous and detailed description of historical discourse. Contemporary trends in historical studies have been defined, according to Foucault, by a crisis in the status of the document as the basis for reading history. How should documents be interpreted? Foucault's answer is not to 'interpret' them at all, and indeed to relocate the basic element of historical study from the document to the statement (which is only loosely bound to the specific document in which it is read).
This redefinition of the document in terms of positively describable statements (and, ultimately, positive discursive formations) means that Foucault must also redefine the historical archive. The archive, then, can no longer be seen simply as a collection of documents, and can no longer be interpreted as the collective knowledge of a given culture or period. Instead, the archive must be seen in terms of the conditions and relations that define statements and discourses; the archive then appears, to archeology at least, not as a set of things but as a set of general rules concerning the longevity of statements. Thus, the archive is defined as 'the general system of the formation and transformation of statements.' Critics of Foucault argue that the archeological method is impossibly (even obsessively) strict about refusing to see the archive as a sign of something else. Foucault wants to describe statements at a semi- scientific, archeological distance (in fact, he notes that this distance is the only thing that allows us to describe an archive accurately). Historical statements are then taken not as signs of something else that the historian must read 'in' them, but as 'monuments' to be described almost as one would describe a physical artifact. Foucault admits that other kinds of analyses of language (like grammar or literary criticism) may have their own validity; he just wants to focus exclusively on the way statements arise and function in discourse. But is such a purifying project really possible? Critics have suggested that this anti- interpretive, 'archeological' distance of the historian from the archive is impossible, and that Foucault is ignoring the discursive conditions by which his own analysis is defined.
The replacement of a psychologized, actual subject of a statement by a subject 'position' built into the statement has proved one of the most transformative ideas to come from Foucault's work. Although the Archeology was written before Foucault's long, intensive engagement with issues of identity and power, it provides the theoretical ground for that later work.
In analyzing discourse in and of itself, the notion that each statement has an author becomes irrelevant (because the author is not a part of the discourse itself). Instead, what archeology finds is that each statement is coded as coming from a specific position within the discursive and institutional field. This position involves a whole host of factors, among which the most crucial for Foucault's later work are those of authority and knowledge. The possibility of making statements that count as knowledge (or as expert opinion, or as scientific fact) depends on a wide range of discursive conditions, from the formation of specific 'objects' of knowledge to the formation of 'strategies' for deploying one theory against another. One such condition is that of the statement's 'enunciative modality,' the specific mode in which it is formulated as coming from a particular subject position.
A given enunciative modality (i.e., a given subject position) does not depend on an attachment to an actual author. One enunciative modality can be used by many authors, and one author can use many different enunciative modalities. Archeology is able to recognize this contingent, variable nature of subject positions because it never looks beyond the statement to an actual, psychological author. The resulting idea, that our identities as agents in discourse are themselves aspects of discourse, has been explosively influential, yielding whole academic fields that examine the discursive constitution of identity.
This can also be a profoundly disturbing idea, because it emphasizes the extent to which our selfhood is scattered beyond us rather than originating with us. Foucault's language in the Archeology notes this dissociative effect: 'Thus conceived, discourse is not the majestically unfolding manifestation of a thinking, knowing, speaking subject, but, on the contrary, a totality, in which the dispersion of the subject and his discontinuity with himself may be determined.'