The excessive pragmatism of American librarians has thus far prevented them from formulating a defensible philosophy of librarianship because their knowledge problems cannot be resolved by action theory. Analysis of the metaphysics, epistemology, and ethics of librarianship shows that its realities consist of the invisible structure of thought, that ideative realities of this sort are immune to empirical study because they cannot be observed, and that human action in relation to such realities is, and must always remain, strictly instrumental. The American system of librarianship is therefore short-circuited at its source, which explains why the physical methods of scientific action theory are thoroughly inappropriate for studying the formal realities of librarianship. (Author/ESR)