To be effective, however, monetary easing must be followed by a comprehensive package on the fiscal side.

Central bank Governor Mark Carney, making good on his post-referendum pledge to ease policy, unveiled measures that included halving the bank's benchmark interest rate to 0.25 percent, boosting its government bond buying and adding corporate debt to its shopping list. His monetary policy committee even suggested another rate cut is on the cards later this year, though Carney ruled out negative rates.

It's clear why the central bank felt it had to act. Britain's services sector, which contributes more to the economy than any other sector, is poised to shrink at its fastest pace since 2009, according to Markit's July survey of purchasing managers published on Wednesday.

To reverse that trend, Chancellor of the Exchequer Philip Hammond has to fulfill his promise to "reset" an economic policy that has centered on austerity in recent years. Central banks all around the world are reaching (and maybe exceeding) the limits of the good that monetary policy can do to resuscitate growth and confidence.