Knowledge has been a defining focus for the curriculum studies field. In the early part of the 21st century convincing arguments were mounted that knowledge needed to be ‘brought back in’, both to the curriculum of schools and to the attention of curriculum researchers. This book is a result of these arguments, and what some regarded as a ‘crisis’ in curriculum study related to the growing emphasis on international comparisons between education systems. The book’s most important contribution is to build on seminal work in the sociology and philosophy of education in order to develop new foundations for curriculum study, using the importance of ‘transactions’ as the context for understanding knowledge in the curriculum. The contributors build on this importance to suggest a rapprochement in the field around the idea of curriculum knowledge as both constructed and real. This book was originally published as a special issue of The Curriculum Journal.