Michel Foucault's intellectual family tree is notoriously hard to trace. Throughout his career, he was hostile to attempts to link him to a particular movement. At some points, he linked himself to the critical philosophy of Immanuel Kant, or to the history of science practiced by his mentor George Canguilhem. Describing the influences on his work is therefore a complicated business. Three influences are particularly important in Discipline and Punish: Friedrich Nietzsche, structuralism, and Foucault's political activism. None entirely explains his project, however.
Foucault and Nietzsche
The influence of Nietzsche on Foucault was considerable, particularly in his student days. Foucault credited Nietzsche with freeing him from the "prison" of Hegelian philosophy and the existentialism and Marxism of Sartre, which represented the dominant French intellectual trend of the 1940s and 1950s. Nietzsche also influenced Foucault's conception of insanity in Madness and Civilization. In simplified form, Nietzsche's philosophy emphasized the coming crisis of religion and morality, and his deep-felt hostility to religion. He was perhaps the first philosopher to argue that "God is dead", and to suggest how man could progress beyond this situation. These methods included a reinterpretation of man and the natural world along more positive lines, and the tracing of a genealogy of morals (in Genealogy of Morals).
This concept of genealogy is perhaps Nietzsche's main legacy to Foucault. Nietzsche's idea of a "genealogy of morals" sought to reinterpret morality "from the perspective of life," praising those qualities that enhanced life, rather than the "herd morality" that detracted from it. In Foucault's work, genealogy became an attempt to examine various discourses from a critical viewpoint. His essay Nietzsche, Genealogy, History presents Foucault's interpretation of Nietzsche's idea of history.
Foucault and Structuralism
Foucault's relationship to the loosely defined movement known as structuralism is complex. He repeatedly denied being a "structuralist," but many critics have nevertheless linked his work to that of structuralist thinkers such as Levi-Strauss, Roland Barthes, Jacques Derrida and Lacan. Structuralism as a movement attempted to study particular philosophical structures and systems of language. It derives from the work of the linguistic theorist de Saussure, who emphasized the role of "signs" in language. Signs are composed of the sounds that "signify" a word, and the object or concept that they signify. Speech and language are a complex interplay of different signs. De Saussure also argued for two different approaches to the history of language: the synchronic and the diachronic. A synchronic study treats structures at a particular moment in time, whereas the diachronic approach is historical.
Many of Foucault's concerns might be described as being "structuralist," such as his interest in the role of language and systems of power in controlling individuals. More importantly, his conception of the individual resembles that of many other structuralists. Although much of Foucault's work is aimed at giving individuals trapped within a particular discourse a "voice", universal ideas of human nature or man are meaningless. For him, the wider structures that control and create man are more important. Discipline and Punish does not claim to be a "structuralist" interpretation of the prison, but reading it in this way may be useful. You should beware of putting Foucault into narrow philosophical categories, however: his attempts to resist definition are important in any interpretation of his work.
Foucault and Political Activism
A more immediate influence is Foucault's involvement in the French campaign for prison reform, GIP (Groupe d'information sur les prisons). As a political activist, Foucault visited prisons in France and America, wrote pamphlets and spoke in pubic about prison conditions. This experience was obviously not the only factor that drove him to write Discipline and Punish, but it shows that his notion of prison life was more than purely theoretical. The book is in many ways an attempt to give a theoretical grounding to what Foucault had seen, to explain the conditions and structures of the places he visited in terms of the operation of power in society.
The Influence of Foucault
Foucault's influence is considerable. This influence is particularly marked in America and is most evident in the adoption of his terminology by other philosophers and historians. The notion of the discourse and of the relationship between power and knowledge are particularly influential. Philosophers have attempted to apply some of Foucault's methods to other areas, such as the history of ideas, feminism, and "postmodernism" (a term Foucault never used). Arguably, many writers do this without considering the implications: Foucault's role as the fashionable theorist of 1980s and 1990s resulted in many bad books allegedly influenced by him.
Criticism of Foucault's methods and conclusions is also widespread. Traditionally, he is accused by historians of mishandling evidence and of ignoring previous work in various fields. Foucault's legendary carelessness with footnotes and references may have something to do with this. Discipline and Punish tends to escape relatively lightly, but formidable opposition is lined up against Foucault: his obscurity, hostility to traditional institutions and sloppy scholarship do not endear him to some people. Indeed, one critic said, "Foucault-bashing is the favorite indoor sport of American academics."