In this dissertation, I perform and compare three different studies of introductory physics students' epistemological views – their views about the nature of knowledge and how it is learned. Physics education research (PER) shows that epistemological views affect how students learn, so they are important to understand and diagnose. The first study uses a Likert-scale instrument, adapted from the Maryland Physics Expectation Survey, designed to assess to what extent students see physics knowledge as coherent (rather than piecemeal), conceptual (rather than just formulas), and constructed (rather than absorbed). Using this survey, I documented several results, including that (i) a large lecture class can produce favorable changes in students' epistemological views, at least in the context of the class, and (ii) teaching a rushed modern physics unit at the end of an introductory sequence can lead to negative epistemological effects. The second study uses the Force Concept Inventory with modified instructions: students indicated both the answer they think a scientist would give and the answer that makes the most sense to them personally. A "split" between these two answers shows that the student does not think she has reconciled her common sense with the formal physics concepts. This study showed that attention to reconciliation in a course allows students to see initially-counterintuitive ideas as making sense. Finally, I did a detailed study of one student by (i) watching video of her in tutorial, where she and three other students answered a structured series of conceptual and quantitative physics questions, (ii) formulating interviews based largely on what I observed in the video, and (iii) interviewing her while the tutorial was still fresh in her head. I repeated this cycle every week for a semester. I found that her tendency to focus on the multiple and ambiguous meanings of words like "force" hampered her ability to reconcile physics concepts with common sense.