Summary Harry Alpert (1912–1977), the US sociologist, is best-known for his directorship of the National Science Foundation's social science programme in the 1950s. This study extends our understanding of Alpert in two main ways: first, by examining the earlier development of his views and career. Beginning with his 1939 biography of Emile Durkheim, we explore the early development of Alpert's views about foundational questions concerning the scientific status of sociology and social science more generally, proper social science methodology, the practical (...) value of social science, the academic institutionalisation of sociology, and the unity-of-science viewpoint. Second, this paper illuminates Alpert's complex involvement with certain tensions in mid-century US social science that were themselves linked to major transformations in national science policy, public patronage, and unequal relations between the social and natural sciences. We show that Alpert's views about the intellectual foundations, practical relevance, and institutional standing of the social sciences were, in some important respects, at odds with his NSF policy work. Although remembered as a quantitative evangelist and advocate for the unity-of-science viewpoint, Alpert was in fact an urbane critic of natural-science envy, social scientific certainty, and what he saw as excessive devotion to quantitative methods. (shrink)