Research suggests that most college and beginning graduate students lack the cognitive complexity required to engage in effective practical and ethical reasoning. Studies on cognitive development support the view that how people approach complex problems varies significantly depending on the underlying epistemic assumptions they use to guide their problem-solving strategies and justify their decisions. We recommend King and Kitchener's Reflective Judgment Model (RJM), a cognitive-developmental framework based on epistemology, as a model for assessing students' current approaches to resolving real-world problems and fostering the skills and dispositions necessary to engage in effective decision making. We discuss strategies for using the RJM to assess students' current epistemic assumptions and to design learning experiences that encourage increased sophistication in ethical problem solving.