  Researchers have argued against deficit-based explanations of students'
troubles with mathematical sense-making, pointing instead to factors such as
epistemology: students' beliefs about the nature of knowledge and learning can
hinder them from activating and integrating productive knowledge they have. But
such explanations run the risk of substituting an epistemological deficit for a
concepts/skills deficit. Our analysis of an undergraduate engineering major
avoids this "deficit trap" by incorporating multiple, context-dependent
epistemological stances into his cognitive dynamics.
