This book offers a comprehensive treatment of the development of Keynes economic ideas in the General Theory of Employment, Interest and Money. It is the first such exclusively economic theory treatment of his career since the Keynes Collected Works were published, and his papers opened to the public. It uses that material, the historical record of the economics of Keynes's time and place and the scholarship available on Keynes's biography and philosophy to build a narrative of his ideas on economic theory from before World War I - when he was lecturing on economics at Cambridge - through the General Theory in 1936. The predominant early influence is Marshall, and Keynes's Marshallian roots are explored in detail. Three themes emerge over his career, each forming a section of the present book and a part of the General Theory: the essentially indeterminancy of labor market analysis, an evolving view of the influence of speculation and trading practices on financial markets and a formal model of the monetary economics of a system that combines these aspects.