Left Radicalism and the Milky Way: Connecting the Scientific and Socialist Virtues of Anton Pannekoek

Anton Pannekoek (1873-1960) was both an influential Marxist and an innovative astronomer. This paper will analyse the various innovative methods that he developed to represent the visual aspect of the Milky Way and the statistical distribution of stars in the galaxy through a framework of epistemic virtues. Doing so will not emphasize the unique aspects of his astronomical research, but also reveal its connections to his left radical brand of Marxism. A crucial feature of Pannekoek's astronomical method was the active role ascribed to astronomers. They were expected to use their intuitive ability to organize data according to the appearance of the Milky Way, while at the same time they had to avoid the influence of personal experience and theoretical presuppositions about the shape of the system. With this method, he produced results that went against the Kapteyn Universe and instead made him the first astronomer in the Netherlands to find supporting evidence for Harlow Shapley's extended galaxy. After exploring Pannekoek's Marxist philosophy, it is argued that both his astronomical method and his interpretation of historical materialism can be seen as strategies developed to make optical use of his particular conception of the human mind.