The inter-war economic experience, particularly the Great Depression, taught two critical lessons. First, government intervention is essential. Industrial societies reliant on mass production require sustained consumption and secure employment, which free markets alone cannot guarantee. State intervention becomes necessary to manage demand, control unemployment, and ensure economic stability. Second, international cooperation is vital. Global economic links necessitate managing international flows of goods, capital, and labor for full employment and stability. Economic isolationism, seen during the Depression, proved disastrous, emphasizing the need for coordinated global efforts for collective well-being.