Critical Theory and Epistemology is a comparison of the major epistemological concerns in the twentieth century with critical theory of the Frankfurt School. I focus on modern epistemology as a theory of and about science that also addresses the social and political aims of scientific enquiry.The critique that the book deploys on the epistemological tendencies of late modernity suggests that the main distinction between Kant and the critical theorists lies in their understanding of rationality. Such a critique can be characterized as the ‘battle’ of modern epistemology for or against the scientifically, socially and politically rational. Thus, arguments of modern epistemology, as articulated by phenomenology, structuralism, poststructuralism, modernists and postmodernists, systems’ theory and critical realism, can certainly be considered ‘modern’ in historical terms, but in essence their concerns are of a pre-modern and pre-scientific nature. In such a manner, we come closer to understanding what constitutes the scientific, philosophy, truth, and whether modern epistemology paves the way for a political epistemology in the twenty-first century.