Scientists use judgment in deciding what and how much data to present in publications but science degrees rarely address this issue. Instead, scientific knowledge is presented as certain and students have limited opportunities to use their own judgment in the laboratory. A consequence of this may be that students approach science with a moral absolutist mindset, believing that science is about learning facts and scientists have little need to exercise ethical judgments in relation to data. Students may also hold different ethical standards for themselves and professional scientists. We draw on data from a first-year science module to show that these views can be challenged by encouraging students to reflect on their own behavior and that of famous scientists in situations with varying degrees of professional ethical ambiguity. We provide evidence of significant transitions in students' thinking, suggesting that reflection on these issues may lead to substantial epistemological and ethical development. By the end of the module, many students had moved from an initial position of certainty to the acceptance of multiple viewpoints or to a more mature understanding of the evidence-based nature of science, as well as gaining the ability to critique decisions and make ethical judgments.