Modern economies are built by businesses that take risk. As Edison’s defense suggests, successful risk-takers need scope to experiment without distraction. Economies lacking institutions to support risk-taking are prone to stagnation.

By securing economic and financial stability, central banks play a key role in promoting the risk-taking that is fundamental to innovation and capital formation. On rare occasions, it is officials’  bold willingness to do “whatever it takes” that does the job. More often, it is a series of moderate, gradual actions. Yet, even then, the understanding that the central bank has the broad capacity to act—and, when necessary, to do so without limit—is a key factor underpinning the stability of the system...