Students' views of the nature of scientific knowledge have been recognized as an important component of science learning environments. In this study, we analyze an extensive data base consisting of 23 students' written and oral discourse about ontology, epistemology, and sociology of scientific knowledge collected over a 15-month period in the context of two consecutive junior- and senior-level physics courses. Over a 2-month period at the beginning of the second year, students read, reflected on, and talked about a text which discusses epistemology in the context of physics. Our study shows that students drew on nine types of discursive resources to support their ontological, epistemological, and sociological claims. Toward the end of the study, the range and number of supportive statements had increased. Simultaneously, few students changed their ontological and sociological claims, but a considerable number changed their epistemological claims. Two case studies illustrate the development of student discourse in the course of the study.