We often think of reason as a fixed entity, as a definitive body of facts that do not change over time. But during the Enlightenment, reason also was seen as a process, as a set of skills enacted on a daily basis. How, why, and where were these skills learned? Concentrating on Scottish students living during the long eighteenth century, this book argues that notebooks were paper machines and that notekeeping was a capability-building exercise that enabled young notekeepers to mobilize everyday handwritten and printed forms of material and visual media in a way that empowered them to judge and enact the enlightened principles they encountered in the classroom. Covering a rich selection of material ranging from simple scribbles to intricate watercolor diagrams, the book reinterprets John Locke's comparison of the mind to a blank piece of paper, the tabula rasa. Although one of the most recognizable metaphors of the British Enlightenment, scholars seldom consider why it was so successful for those who used it. Each chapter uses one core notekeeping skill to reveal the fascinating world of material culture that enabled students in the arts, sciences, and humanities to transform the tabula rasa metaphor into a dynamic cognitive model. Starting in the home, moving to schools, and ending with universities, the book reconstructs the relationship between media and the mind from the bottom up. It reveals that the cognitive skills required to make and use notebooks were not simply aids to reason; rather, they were part of reason itself.