Like most of Foucault's works, Madness and Civilization was highly interdisciplinary in nature. On the one hand, it was a history, one which traced the development of the concept of madness from medieval Europe to the present day. Like all histories, Foucault detected change over time, with mental illness becoming increasingly repressed in Western society, a process he memorably called the "great confinement." According to Foucault:
We have yet to write the history of that other form of madness, by which men, in a sovereign act of reason, confine their neighbors, and communicate and recognize each other through the merciless language of non-madness...
Foucault claimed to be writing that history. On the other hand, his work was deeply suffused with psychology, and took a strongly sociological position on madness, that is, it was the creation of society, rather than an objective medical condition. The interesting thing about Madness and Civilization from an interdisciplinary standpoint is that Foucault was using history to show how other disciplines, especially psychology, developed as a means of identifying, ostracizing, and confining people that were "mad." This process saw changes in the definition of what exactly "mad" was, most notably during the Enlightenment, when "madness" was juxtaposed in the European mind with "reason."
The most chilling aspect of his argument, and the part that is perhaps the most psychological in its own right, is that people who displayed "abnormal behavior" were expected to recognize their own madness, internalize a definition of what it meant to be "sane," and commit themselves to receiving treatment (or punishment) which Foucault equates with the exercise of power over the minds of people.