We can see good economic policies in the context of a consistent analysis of the economy. - Peter Temin

Modern macroeconomics flourished in its pursuit of the secrets of long-run economic growth, but it neglected short-run economic problems. In the long run, prices are flexible, and the growth of the economy is determined by the growth in the ability to supply goods and services. But in the short run prices are not flexible. Growth can be held back because prices are too high and, as a result, demand is too low. Keynes made his name by analyzing short-run problems caused by the stickiness or even rigidity of some important prices. But these Keynesian ideas were abandoned by modern macroeconomics.

Central banks have moved to stimulate spending in the face of this attempt to increase savings by lowering interest rates. They lowered them to the zero lower bound without having much effect; the fall in desired savings was too large. We are in a Keynesian liquidity trap. Central banks have tried to stimulate spending by actively increasing the money supply, raising fears of inflation in many circles. But no inflation has resulted as the cash sits idle in corporate coffers. Even at zero interest rates, business firms are reluctant to spend!
What to do? Many pundits say we must simply endure what they call secular stagnation. This is an unhappy prediction. Much better is the Keynesian insight that this is the perfect time for fiscal policy. In the U.S. again, there are immediate needs to repair roads and bridges, rebuild the energy grid, and modernize other means of travel. Keynesian fiscal policy expansion will benefit the economy in both the short and long run.