Paula Worth presents in this article a means of challenging students' tendency to generalise even when they know that they should not. How can teachers encourage their students to say something meaningful about the past while avoiding making unwarranted generalisations? Worth takes teachers through the process of planning her own enquiry designed to do this while teaching students about the Age of Discovery. She begins with the familiar realisation, prompted by her assessment of her students' work, that all is not quite well, and then explains (via the work of several authors familiar to readers of this journal, a visit to www.activehistory.co.uk, liaison with other departments and several cups of coffee) how she plans lessons designed to sharpen up her pupils' appreciation of a key historical concept. The result is a decision-making activity which leaves her students a little less certain about what actually happened in the past--but aware, as historians should be, of the limitations of historical knowledge.