Historical writing on science in the United States is essentially, although not entirely, a post-World War II phenomenon. Characteristic of that writing is the recognition that science is a human activity carried out within a particular cultural and political context. For most Americanists, the proper subjects of historical research are humans and their institutions, not the evolution of abstract scientific ideas, and to understand the history of science, the historian must also understand the history of the nation within which the science was practised.