In this article, I deconstruct the concept of understanding in mathematics education, examining how it is spoken into being and what work it does for primary school student teachers. I use poststructural analysis to unpack interviews with a student teacher, Jane, drawn from a larger longitudinal study. I show how she negotiates tensions between "romantic" discourses of understanding within mathematics education research and "functional" discourses of understanding within neoliberal mathematics education policy. A romantic discourse constructs understanding as an aspect of being resulting from the natural curiosity of the child. A functional discourse constructs understanding as performances within which the child is indistinguishable from automata. I argue that Jane takes on both functionality and romanticism, but they collide creating a disorderly discourse of understanding that reproduces inequity.