Fed chairman Jerome Powell is increasingly under fire for his apparently inability to take inflation seriously or admit it may be more than “transitory.” There’s been much talk of tapering the Fed’s enormous asset purchases, yet—as is typical for the Fed, actual action remains scheduled for some nonspecific time in the future. And if the economy weakens, as an increasing number of observers expect it to do, the Fed will surely chicken out on tapering and keep the money spigots open. Yet as recently as August the Fed and its officials routinely warned that there wasn’t enough inflation and...