ZIRP also makes the Fed an indispensable enabler of big government. By making borrowing, and hence deficits, cheap, ZIRP facilitates the political class’s bipartisan strategy of delivering current benefits while deferring costs. ZIRP also provides cheap credit to big government’s partner, big business.

Originally, in 1913, the Fed’s mission was price stability — preserving the currency as a store of value. In 1977, Congress created the “dual mandate,” instructing the Fed to maximize employment. This supposedly authorizes the Fed to manipulate the stock market, part of Bernanke’s inflation of the dual mandate into “promoting a healthy economy.” Is a particular distribution of income unhealthy? The Fed will tell us.

The next Fed chair will put her or his hand on the economy’s imaginary tiller after politically muscular constituencies campaigned for her or his candidacy. What will this helmsman do when, say, the homebuilders and others in the construction industry clamor preemptively against any retreat from ZIRP?

The Fed has become the model of applied progressivism, under which power flows to clever regulators who operate independent of political control. The Fed is, however, a creation of Congress, which may not forever refrain from putting a bridle and snaffle on a Fed that increasingly allocates credit, wealth and opportunity.