The processes by which ideas, objects, texts and political thought and experience moved across boundaries in the Middle Ages form the focus of this book, which also seeks to reassess the nature of the boundaries themselves; it thus appropriately reflects a major theme of Dr Malcolm Vale's work, which the essays collected here honour. They suggest ways of breaking down established historiographical paradigms of Europe as a set of distinct polities, achieving a more nuanced picture in which people and objects were constantly moving, and challenging previous conceptions of units and borders. The first section examines the construction of boundaries and units in the later Middle Ages, via topics ranging from linguistic units to social stratifications, and geographically from the Netherlands and Scotland to Gascony and the Iberian peninsula; it reveals how much the relationship between exchange and boundaries was reciprocal. The second section considers the mechanisms by which it took place, from West Africa to Italy and Flanders, and discusses the actual exchange of people, texts, and unusual artefacts. Overall, the essays bear witness to the constant interplay and interconnections throughout medieval Europe and beyond. Contributors: Paul Booth, Maria Joa?o Violante Branco, Rita Costa-Gomes, Mario Damen, Jan Dumolyn, Jean Dunbabin, Jean-Philippe Genet, Michael Jones, Maurice Keen, Fre?de?rique Lachaud, Patrick Lantschner, Guilhem Pe?pin, R.L.J. Shaw, Hannah Skoda, Erik Spindler, John Watts.