This chapter reconstructs critical theory's engagement with instrumental reason and explicates why the critique of instrumental reason was so central to the work of the first generation of critical theorists and how it posed conundrums that motivated Habermas's work. The first section deals with the intellectual sources upon which critical theorists drew in developing the critique of instrumental reason, focusing particularly on Max Weber and Georg Lukács. The author then discusses the critique of instrumental reason advanced by the critical theorists, focusing on the figures who most explicitly dealt with the problem, Horkheimer, Adorno, and Marcuse, and deals with the problem of instrumental reason as it applies to issues of social scientific method, the Enlightenment, culture, and technology. The third section looks at solutions to the problem of instrumental reason, examining Adorno's concept of the negative dialectic, Marcuse's political vision, and, finally, the emergence of Habermas's theory of communicative reason. The author concludes by discussing the relevance of critical theory's engagement with instrumental reason in light of contemporary debates in the social sciences.