THIS book is not a history of knowledge – learning's content – it is a history of processes (some in their own way political) about the interactions and relations among learned people, their concepts and the institutions to which they belonged. Relations, processes: they cannot be observed directly. Yet, this study shrinks from that species of thought that regards itself as social constructivism or social determinism because it pays particular attention to agency and contingency. Politics and war are among the contingencies that are particularly important in shaping the relations and processes shaping knowledge in the twentieth century and so it is to those contingencies that this study now turns. Politics and war hardened the epistemological edges of knowledge in twentieth-century Britain. They hardened those edges because the demands of politics and war reinforced latent stifling positivism in learned life. War and politics gave a kind of public legitimacy for which people of learning longed but, thereby, turning their learning in a more applied and utilitarian direction robbed them of intellectual autonomy and independence. The issues and incidents that this chapter discusses – patri-otism and loyalty during the Great War; the encounter of British people of learning with Soviet scholars at the International Congress of the History of Science; the unwillingness to admit Charles Singer, the historian of science, to their fellowships by both the Royal Society and the British Academy;