This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book distinguishes between the processes of explanation and those involved in understanding. It reviews the way that archaeological materials became accepted as the testimonies for the existence of a now absent, but nonetheless singular humanity. The book discusses the various ways that archaeology has, since the 1950s, been used to explain the order observed amongst archaeological residues, not as sequences comprising individual cultural traits but in terms of the systematic organisation of the past, firstly with reference to the system’s adaptation to available ecological resources, secondly with reference to the logic of its social organisation, and thirdly with reference to the way that human systems were likely to have been structured by the cognitive perceptions of their members.