Most research on personal epistemologies has conceived them as made up of relatively large, coherent, and stable cognitive structures, either developmental stages or beliefs (perhaps organized into theories). Recent work has challenged these views, arguing that personal epistemologies are better understood as made up of finer grained cognitive resources whose activation depends sensitively on context. In this article, we compare these different frameworks, focusing on their instructional implications by using them to analyze a third-grade teacher's epistemologically motivated intervention and its effect on her students. We argue that the resources framework has more predictive and explanatory power than stage- and beliefs-based frameworks do.