This is a paper on interdisciplinarity and rhetoric. Neuroeconomics is hype, but this does not rule out entertaining hopes about its capacity to produce some desirable consequences. Its 'disciplinary conventions' are characterized as those of a young interdisciplinary field. Its rhetorical advantages are identified, and its rhetorical excesses are put in perspective and conditionally excused. Its evidential roles are emphasized, and they are shown to be limited in alleviating the under-constraint issue due to the difficulty of using fMRI properly.