What is jewellery? This new publication is a reflection on that question. Here is an interdisciplinary approach transcending the familiar categories crafts or art, applied or fine. What matters here is exploring what jewellery is - not what it looks like. ''Thinking Jewellery'' is the distilled result of a colloquium with the same title that has been jointly hosted since 2005 by the Idar-Oberstein course in gem and jewellery design by Trier Polytechnic and the city of Idar-Oberstein. Each year in May more than a hundred jewellery designers, students and academics from all over Europe convene in Idar-Oberstein to conduct a comprehensive discourse without boundaries on the theoretical foundations of jewellery. This publication contains the most interesting lectures given over the five years since major artists in jewellery, distinguished ethnologists, philosophers, psychologists, cultural anthropologists, and scientists instituted the Colloquium. Lavishly illustrated to showcase the objects discussed, it documents the standards so spectacularly achieved by the Idar-Oberstein Jewellery Institute.''Thinking Jewellery'' fascinatingly exemplifies the productive interaction of theoretical reflection and practical execution.