The impact of Habermas's work in this area derives from his sustained efforts to formulate a defensible response to the philosophical developments definitive of the contemporary era. As is well known, Habermas develops his theory of communicative rationality in response to the philosophical paradigm shift generated by the demise of the 'philosophy of the subject', definitive of modem philosophy since Descartes. In a distinctive variation on the 'linguistic turn' undertaken by other influential contemporary philosophers, he focuses attention on the structures of 'communicative interaction'. For many critics, the core problem with Habermas's communicative approach is epitomized by his enshrining of the concept of an 'ideal speech situation' as a pivotal feature of his epistemology. For embrace of this and the related idealizations seems to connote the possibility of attaining an idealized standpoint from which we could test the epistemic credentials of proffered knowledge claims by idealized means.