There has been a marked tendency towards fragmented specialization in the field of development studies over the last two decades, as economists became increasingly interested in isolated details regarding development issues, losing sight of the relevance of these problems to the overallprocess of socio-economic development. Adopting a critical attitude towards such a trend, this book discusses a broad range of theories of economic development and underdevelopment, while emphasizing the usefulness of holistic approaches that view development as a historical process.Our journey starts with the relevant literature from Marx and Lenin, to neoclassical theories of international trade and the critique by the ECLA school under Raul Prebisch, and onward to the dependency theorists -- Gunder Frank, Amin and Wallerstein. This book deals in some detail with W.A. Lewis'dualism theory that focused on the internal relationship within the underdeveloped economy, the extensions of his model by Jorgenson, Fei and Ranis, and Harris and Todaro, and Nicholas Kaldor's seminal contributions to dualism. It also comprehensively covers the question of determination of theagricultural surplus in analysing the significance of the role of agriculture and agricultural surplus in the process of development.There is no one book that deals with the significant schools of thought within development economics. With its extraordinary wide scope, senior undergraduate and postgraduate students of economics, teachers and researchers will find this an invaluable and fascinating journey.