In The Archaeology of Knowledge (1969), Foucault showed how the sciences themselves are constituted by “discourses,” or background ways of forming and transmitting knowledge. Without prior standards that make scientific knowledge acceptable as knowledge, scientific discoveries would have no importance. For example, if we hear that scientists have discovered a gene that predisposes people to a certain kind of cancer, we accept this as true, because we accept the authority of science. Discipline and Punish: The Origin of the Prison (1975) marks the beginning of Foucault’s investigation of power. He argued that institutions such as the prison, the army, the factory, and the school wield power through specific techniques in which oppression can coexist with representative democratic political structures.

Foucault’s philosophy was mainly social criticism rather than the theory of self-creation associated with existentialism. However, in his own life, he became notorious for unconventional and spontaneous behavior in ways that the public has associated with existentialism. During the last years of his life, Foucault was active in the world in ways that some found shocking, both politically and personally. In a late interview he said, “Well, do you think I have worked all these years to say the same thing and not be changed?”

Foucault first visited the United States in 1970 to lecture at the University at Buffalo, State University of New York, later visiting the University of California, Berkeley. He took LSD at Zabriskie Point in Death Valley National Park, and referred to the experience as life changing in positive ways. In the late 1950s, he went to Iran, and after the revolution he supported the new reactionary government. His essays about Iran, published in the Italian newspaper Corriere della Sera, provoked controversy when they were translated into French and English in 1994 and 2005, respectively.

Foucault was in a committed 25-year relationship with Daniel Defert, a former student. He described it as having lived in “a state of passion,” adding that “at some moments this passion has taken the form of love.” Much has been said and written about Foucault’s exploration of homosexual bars and sex clubs in the Castro district of San Francisco. Foucault died of an AIDS-related infection, although this was not admitted at first, when his death was announced in Le Monde. Before he died, Foucault destroyed massive amounts of his unpublished writings and directed that other manuscripts be destroyed also.