When the Federal Reserve slashed its discount rate by a half-percentage point earlier this month, it was trying to add a little lubricant to a credit market that seemed on the verge of seizing up. But by giving weary investors a chance to catch their breath, the move also gave them an opportunity for finger pointing – at avaricious mortgage lenders, at naive borrowers, and at rating agencies.

One culprit, though, has not only avoided blame but has come across as the episode's hero. And that culprit is the Federal Reserve itself. Like some renegade fireman, though unwittingly, the Fed played a part in igniting the conflagration it's now trying to smother.

Because the disaster was kindled years ago, responsibility for it belongs not to the current Fed board but to Alan Greenspan and his team of monetary policymakers. The fundamental problem, however, transcends the actions of any Fed chairman. Indeed, the Fed as it's presently managed can hardly help causing sometimes ruinous market distortions.

Why did mortgage lenders earlier this decade start showering credit as if it were spewing from a public fountain? The answer is that credit was spewing from a public fountain – and that fountain was the Fed. In December 2000, the Fed began an unprecedented year-long series of rate cuts, reducing the federal funds rate from over 6 percent to just 1-3/4 percent – a level last seen in the 1950s. By mid-2003, two further cuts had reduced the rate to just 1 percent.

The general aim of these cuts was to keep a mild growth slowdown from getting worse. But they had the quite unintended effect of generating euphoria in the mortgage market by flooding it with funds. Lenders dramatically lowered mortgage rates and kissed old-fashioned lending standards goodbye. Buying property was never easier. As one jubilant industry insider put it, "Who could ask for anything more?"

The sad sequel is grist for the mill of monetary economists long critical of central banks' attempts at fine-tuning. It illustrates the late Milton Friedman's claim that the full effects of monetary policy changes happen only after "long and variable lags," when conditions that motivated the changes have passed into history. The result is that fine-tuning often ends up promoting business cycles instead of dampening them.

The subprime lending crisis also shows that, while central banks certainly have the power to expand a nation's spending power, they can't guarantee that the extra power gets used as intended, namely, to give a roughly uniform boost to the overall demand for goods. On the contrary: The crisis supports the argument, first developed by Austrian-school economists Ludwig von Mises and Friedrich Hayek, that the techniques central banks employ to increase spending power are bound to distort spending patterns by driving lending rates below their sustainable, "natural" levels.

By injecting the new money they create into credit markets, central banks create an artificially high demand for long-term investments, such as real estate, in which interest costs loom large. Think back a few years. Even your auto mechanic was bragging about "flipping" condos with easy credit. That's a natural consequence of the way central banks distort spending patterns. The trouble, however, is that the new money does eventually swell overall demand, including the demand for credit. Interest rates soon rise, ending the investment boom. Regrets multiply.

That's exactly what happened last year, when the federal funds rate climbed back above 5 percent.

In hindsight, it's easy to say that the Fed blundered. But avoiding similar blunders in the future is another matter. The truth is that the Fed, as presently constituted, faces an impossible task: It can't tell whether its targeted rates are "natural" (and therefore sustainable) except in retrospect, when it's too late; and it will always be tempted to engage in fine-tuning, both because the Humphrey-Hawkins Act of 1978 calls for it to do so, and because a myopic and inadequately informed public rewards Fed bureaucrats for "doing something" even when they ought to stand pat.

Only institutional reform can get us out of this predicament. The Fed must be taken out of the fine-tuning business. Instead, it must observe a strict and unambiguous monetary rule, such as one calling for the Fed to announce and stick to an inflation-rate target. As it happens, chairman Ben Bernanke favors such a rule. If Congress gives him what he wants, the Fed may be spared some future finger pointing; and the public may be spared further crises.

• George Selgin is a professor of economics at the University of Georgia's Terry College of Business.