The debate between Marcuse and Habermas over technology marked a significant turning point in the history of the Frankfurt School. After the 1960s Habermas's influence grew as Marcuse's declined and Critical Theory adopted a far less utopian stance. Recently there has been a revival of quite radical technology criticism in the environmental movement and under the influence of Foucault and constructivism. This article takes a new look at the earlier debate from the standpoint of these recent developments. While much of Habermas's argument remains persuasive, his defense of modernity now seems to concede far too much to the claims of autonomous technology. His essentialist picture of technology as an application of a purely instrumental form of nonsocial rationality is less plausible after a decade of historicizing research in technology studies. The article argues that Marcuse was right after all to claim that technology is socially determined even if he was unable to develop his insight fruitfully. The article derives a new approach to technology criticism from both constructivism and Habermas's communication theory. The essence of technology is shown to be historical and reflexive, like the essence of other social institutions. As such an institution, its rationality is always implemented in value-biased forms subject to political critique.