  Critical Theory in the narrow sense has had many different aspects and quite distinct historical phases that cross several generations, from the effective start of the Institute for Social Research in the years 1929–1930, which saw the arrival of the Frankfurt School philosophers and an inaugural lecture by Horkheimer, to the present. Its distinctiveness as a philosophical approach that extends to ethics, political philosophy, and the philosophy of history is most apparent when considered in light of the history of the philosophy of the social sciences. Critical Theorists have long sought to distinguish their aims, methods, theories, and forms of explanation from standard understandings in both the natural and the social sciences. Instead, they have claimed that social inquiry ought to combine rather than separate the poles of philosophy and the social sciences: explanation and understanding, structure and agency, regularity and normativity.  Such an approach, Critical Theorists argue, permits their enterprise to be practical in a distinctively moral (rather than instrumental) sense. They do not merely seek to provide the means to achieve some independent goal, but rather (as in Horkheimer’s famous definition mentioned above) seek “human emancipation” in circumstances of domination and oppression. This normative task cannot be accomplished apart from the interplay between philosophy and social science through interdisciplinary empirical social research (Horkheimer 1993). While Critical Theory is often thought of narrowly as referring to the Frankfurt School that begins with Horkheimer and Adorno and stretches to Marcuse and Habermas, any philosophical approach with similar practical aims could be called a “critical theory,” including feminism, critical race theory, and some forms of post-colonial criticism. In the following, Critical Theory when capitalized refers only to the Frankfurt School. All other uses of the term are meant in the broader sense and thus not capitalized. When used in the singular, “a critical theory” is not capitalized, even when the theory is developed by members of the Frankfurt School in the context of their overall project of Critical Theory.