Positivism and the critique of positivism becomes an issue in the history of critical theory on two occasions: first, in the 1930s, when Horkheimer and Adorno enter into a discussion with the Vienna Circle of logical positivism, and later in the 1960s when Adorno debates the critical rationalism of Karl Popper. To critical theory the critique of positivism becomes important not only because it is an issue in the philosophy of science. Positivism is also viewed as an obstacle to a critical approach to society, limiting the analysis to what is quantitative, measurable and empirically observable. In this chapter, I will first sketch the tradition of positivism in social science and the relation of Marxism to positivism. I will then introduce Horkheimer’s central essay from the 1930s and its twofold critique of positivism’s epistemology and politics. This discussion ended with a complete break between the Frankfurt School and the Vienna Circle. The positivist dispute of the 1960s between Adorno and Popper is then presented. It did expose some common ground between Adorno and Popper, but also important differences. Popper’s alternative to positivism is too limited and has not left the scientistic ideal for social sciences behind. Adorno also advocates a concept of critique that unlike Popper’s critical rationalism is also a critique of society, not just of theories.