Max Horkheimer, one of the founders of the Frankfurt Institute of Social Research established in 1923, coined the term critical theory in 1937. While the school failed to produce what could be called a systematic theory, it drew on, and interweaved, various philosophical strands and prominent themes of political and social thought, including historical materialism (Marxism/Western Marxism), Freudian analysis, cultural disenchantment, Hegelian dialectics, and totality. Yet by the 1940s, many of the first-generation Frankfurt school thinkers sought to counter the emasculation of critical reason, dialectics, and self-conscious theory with a focus on the negativity of dialectics. Later critics would claim that they had abandoned the progressive platform of the Enlightenment, or the project of emancipation from social and political oppression. In the 1980s, Jürgen Habermas’s communicative action theory would provide a so-called critical turn in Frankfurt school critical theory by resituating reason and social action in linguistics. It was during this time that international relations (IR) theorists would draw on Habermas’s theory and that of other critical theorists to critique the limits of realism, the dominant structural paradigm of international relations at the time. The first stages of this critical theory intervention in international relations included the seminal works of Robert Cox, Richard Ashley, Mark Hoffman, and Andrew Linklater. Linklater, perhaps more than any other critical IR theorist, was instrumental in repositioning the emancipatory project in IR theory, interweaving various social and normative strands of critical thought. As such, two seemingly divergent critical IR theory approaches emerged: one that would emphasize the role of universal principles, dialogue, and difference; the other focusing predominantly on the revolutionary transformation of social relations and the state in international political economy (historical materialism). Together, these critical interventions reflected an important “third debate” (or “fourth,” if one counts the earlier inter-paradigm debate) in IR concerning the opposition between epistemology (representation and interpretation) and ontology (science and immutable structures). Perhaps more importantly, they stressed the need to take stock of the growing pluralism in the field and what this meant for understanding and interpreting the growing complexity of global politics (i.e., the rising influence of technology, human rights and democracy, and nonstate actors). The increasing emphasis on promoting a “rigorous pluralism,” then, would encompass an array of critical investigations into the transformation of social relations, norms, and identities in international relations. These now include, most notably, critical globalization studies, critical security studies, feminism, postmodernism, and postcolonialism.