CalPundit has an easy introduction to Keynesian economics, pointing out that ‘we are all Keynesians now’.

To clarify this, nearly everyone accepts that the public sector acts, and should act, as an economic stabiliser by allowing tax revenues to decline and expenditure to rise during recessions (and the opposite during booms). Most economic policymakers are willing to supplement the automatic stabilisation arising from the tax-transfer system with some discretionary fiscal stimulus during recessions.