In this book, Prof. F.A. Ilesanmi presented intervention as an act of God and the ultimate purpose of the Urban and Regional Planning profession. He argued that the rationale for intervention is to bring about growth, development, progress, prosperity, improved living standard, livability and happiness – all these being technically different and hierarchical. Making references to diverse measures of these concept, he used those of the United Nations Development Programme (UNDP), CEBR, Legatum and Forbe, the author showed that ECOWAS Member States are generally lowly placed at the bottom of the ladder in terms of human development, prosperity and happiness, hence the need for ECOWAS Intervention based on the ECOWAS Treaty as revised. He recommended among other things, a Ten-Year Ten-Sector Intervention Plan for ECOWAS with a Directorate of Intervention to prosecute same.