Technosystem: The Social Life of Reason is a philosophical reflection on the technified world in which we live. Ours is a world of technical systems designed in accordance with technical disciplines and operated by personnel trained in those disciplines. This is a unique form of social organization that largely determines our way of life. Technosystem builds a theory of both the threats of technocratic modernity and the potential for democratic change.Technosystem draws on the tradition of social criticism represented by Herbert Marcuse and the Frankfurt School. These radical thinkers recognized the dystopian implications of the generalization of instrumental rationality but they did not advance a convincing alternative to the new forms of domination imposed by rational systems. That is the contribution of the empirically informed approaches of Science, Technology, and Society Studies (STS). Technosystem uses these approaches to reconcile the new power of rationality with the agency of a public increasingly mobilized to intervene in technical life. In STS this is called “co-production.” The application of this concept in Technosystem recognizes emerging forms of resistance, such as protests and hacking, as essential expressions of public life in the “rational society.”Combining the most salient insights from critical theory with the empirical findings of STS, Technosystem advances the philosophical debate over the nature and practice of reason in modern society. The book offers lucid explanations of the theories of leading figures in both traditions. Neither tradition is sufficient by itself but together they offer deep insight into contemporary experience in technologically advanced societies.