To go by the statements of most mainstream economists, one would be forgiven for believing this is the best of times for Keynesian economics.

Fans of John Maynard Keynes, the renowned early 20th-century economist who developed the theory on how nations could dig themselves out of an economic downturn, have been running victory laps since the collapse last month of the claim by the Harvard economists Carmen M. Reinhart and Kenneth S. Rogoff that economies tend to slow significantly after government debt reaches 90 percent of gross domestic product.

Then, as if on cue, the number-crunchers in Brussels announced last week that the economy of the euro area countries — which have been following a decidedly non-Keynesian path — shrank yet again at the beginning of the year. It was the region’s sixth quarterly contraction in a row.

The confluence of events provided further evidence of Keynes’s central proposition: when consumers and businesses set out to reduce their debt burden, and private spending and investment stall, it is the government’s job to borrow, spend and pick up the slack.