But wait: Then came a survey by the European Central Bank showing that commercial banks in the eurozone are becoming more willing to lend. That information bolstered economists who believe that recent signs of slowing growth reflect temporary factors, like an especially pernicious flu season that kept many workers home and hurt business.

Amid so much uncertainty, Mr. Draghi’s view of growth is critical. He has a large staff of experts and access to data not available to private sector economists, not to mention a doctorate in economics from the Massachusetts Institute of Technology.

And unlike the view of your average economist, Mr. Draghi’s is partly self-fulfilling. If he displays confidence, banks will be more eager to lend, businesses may be more willing to invest in expansion and to hire more people and, lo, it will be so.

For financial markets, the key question in the weeks to come is whether recent economic data will alter the European Central Bank’s schedule for ending the measures it used to keep the eurozone together during an existential debt crisis. Chiefly, the bank bought hundreds of billions of euros in government and corporate bonds as a way of pumping money into the economy.

In recent months, the Governing Council has been making subtle changes in the statements it issues after monetary policy meetings as a way of preparing investors for an end to the bond buying, known as quantitative easing. On Thursday, it left monetary policy unchanged, and made no major changes to its statement.

September is expected to be the last month of the purchases, though the bank will continue to reinvest money it gets back when bonds mature. The aim is to gently bring monetary policy back to normal. Sometime late next year, or maybe not even until 2020, the European Central Bank will then probably begin raising its benchmark interest rates, currently at a historic low of zero, for the first time since 2011.

Any indication by the Governing Council that it is revising its timetable would be big news. But the council takes the long view and has shown in recent months that it won’t be thrown off course by a few unsettling economic indicators.