This paper has two aims, as an exposition of Jürgen Habermas's response to the work of Michel Foucault, and to engage in and assess this debate between two influential contemporary schools of Continental philosophy. Habermas locates Foucault's project in the history of several attempts at a totalizing critique of reason, attempts which are trapped in a performative self?contradiction. Habermas also argues that Foucault is still caught up in the conceptual straitjacket of the philosophy of the subject which his theory was (...) meant to overcome. He shows that Foucault's central notion of power is used in two different and ultimately irreconcilable ways ? as a transcendental as well as an empirical concept. Much of Habermas's critique is justified and could, indeed, be extended to Foucault's anti?realist relativism, but Habermas's own defence of rationalism is not without difficulties of its own. Thus his notion of knowledge?guiding interests commits him to a form of anti?realism and a transcendental concept of instrumental power which is almost as problematic in its consequences as the anti?realism of Foucault. (shrink)