Since the end of the nineteenth century, unreason no longer manifests itself except in the lightning flash of works such as those of Hoederlin, of Nerval, of Nietzsche, or of Artaud.

This quote illustrates a central theme of the work: the idea of madness and art. Confinement in the classical period silences both madness and unreason, so that the only way they can speak is through the work of certain writers. For Foucault, these writers represent the only way to experience or understand unreason in the modern world; unreason is a hidden undercurrent that only breaks through to the surface at certain points. Although the madness of Nietzsche and Artaud has a complex and destructive relationship to their work, their writing offers a rare chance to hear the unreasonable speak. It is the closest the modern world can get to the experience of the Renaissance, when unreason and madness were fully integrated into the world.