This chapter examines the evolution of ‘fragile’ and ‘failed’ state terminology noting the background to the ideas and examining the theorisation around the concepts, before surveying the literature on development in ‘fragile’ and ‘failed’ states in some depth. The OECD Principles for Good International Engagement in Fragile States and Situations are examined in particular, together with the follow-up OECD fragile state evaluations and related literature, as the primary and often normative guidance on development in ‘fragile’ or ‘failed’ states. A range of alternatives and critiques are explored. This chapter, therefore, sets the literature and theory in place as a backdrop for the diversity of case studies presented in Part II of this volume.