The Great Depression brought John Maynard Keynes to the forefront of economic thought. The key "Keynesian" insight was that private investment spending is inherently unstable--due to fads and fashions among investors, or because of shifts in the "animal spirits" of businessmen, or because falling prices disrupt the financial system.
Keynesians thought that prudent monetary policy--central banks raising and lowering interest rates to diminish fluctuations in private investment spending--could go part of the way toward stabilizing the economy. But they also believed that government had to be willing to step in directly, through expansive fiscal policy, to keep the overall level of spending in an economy stable. Such a policy, they believed, would forever banish the specter of large-scale mass unemployment, as in the Great Depression. Moreover, near-full employment might effectively be guaranteed.
The Keynesians foresaw that near-full employment raised the threat of inflation. After all, why should workers and unions moderate wage demands if governments will boost spending whenever high unemployment looms? One big curb on high wage demands--fear of being let go when unemployment rises--was gone. What would replace it?
For the first post-1945 generation, the predominant answer was that corporatist social democracy would replace it. Unions would bow to government requests to moderate their demands for wage increases, and governments would bow to union demands for public spending and social insurance.