This paper traces the perceptions of the agricultural sector held by economists over the last three centuries, with particular emphasis on how the evolution of these ideas has influenced the state of present-day thinking about the economic role of agriculture in developed and developing economies. The paper begins with the seventeenth and eighteenth centuries, leading to a consideration of the place of agriculture in the work of the major figures of classical political economy from Adam Smith to Marx. The rise of neo-classical economics, and its influence on twentieth century thinking, is discussed. In the contemporary period, particular attention is paid to agriculture in development theory, with an assessment of conflicting theoretical ideas about the role of the agricultural sector during the process of economic transformation and growth. The paper concludes with a consideration of the current state of economic thought about the role of agriculture in the economy, and makes some observations on likely future directions.