This influential economic treatise presents a groundbreaking theory that challenges classical economics, asserting that aggregate demand, driven by public and private sector spending, is the primary factor influencing economic activity and employment levels. The book also introduces the concept of fiscal and monetary policies as tools to manage economic downturns, thus shaping the foundation of modern macroeconomics. It further critiques the idea that market economies would automatically provide full employment and argues for active government intervention to prevent economic recessions and depressions.