The Cartesian cogito - the principle articulated by Descartes that "I think, therefore I am" - is often hailed as the precursor of modern science. At the same time, the cogito's agent, the ego, is sometimes feared as the agency of manipulative domination responsible for all present woes, from patriarchal oppression to ecological catastrophes. Cogito and the Unconscious explores the vicissitudes of the cogito and shows that psychoanalyses can render visible a constitutive madness within modern philosophy, the point at which "I think, therefore I am" becomes obsessional neurosis characterized by "If I stop thinking, I will cease to exist."