The convoluted relationship between madness and art is explored, but never fully explained in Madness and Civilization. The work shows Foucault's interest in literature, and his belief in the importance of using literary works as sources in a historical or sociological work. His discussion of madness in the Renaissance, for example, draws heavily on the works of William Shakespeare and Miguel de Cervantes. For Foucault, the fictional character of King Lear reveals much about the role of madness in society.

Foucault’s central argument, however, rests on the idea that modern medicine and psychiatry fail to listen to the voice of the mad, or to unreason. According to Foucault, neither medicine nor psychoanalysis offers a chance of understanding unreason. To do this, we need to look to the work of “mad” authors such as Nietzsche, Nerval and Artaud. Unreason exists below the surface of modern society, only occasionally breaking through in such works. But within works of art inspired by madness, complex processes operate. Madness is linked to creativity, yet it destroys the work of art. The work of art can reveal the presence of unreason, but unreason is the end of the work of art. This idea partly derives from Foucault’s love of contradiction, but he feels that it reveals much about modern creativity.