The introductory chapter presents the problem posed for all Buddhists by the existence of differing versions of what the Buddha taught, preserved by different early schools of Buddhism, in different languages. Using specific examples, it shows how by focussing on these very textual discrepancies, the methodology of comparative analysis to be applied in this book can actually reveal what is most likely to have been the Buddha’s original teaching. A discussion follows of the assumptions underlying this methodology and how it might be applied to core components of Buddhist doctrine. The chapter concludes by showing how the structure of the book is defined by the fourth of the Buddha’s four noble truths, which specifies the path of practice to be followed to end suffering and attain enlightenment.