Arc’s Companions programme includes curated volumes that have a global perspective and that earn their shelf space by their authoritative and comprehensive content, up-to-date information, accessibility, and relevance. As well as providing an overview of the topics, contributing authors are encouraged to challenge the status quo, and recognise contentious issues and cutting-edge concerns. The Companions acknowledge diversity and inclusivity, and open students up to the idea that research is evolving, debatable, and contested and not always definitive.