WASHINGTON -- The White House used the front page of Monday's Washington Post to cashier a Cabinet member. A story headlined ``Bush to Change Economic Team'' said: ``One senior administration official said Treasury Secretary John W. Snow can stay as long as he wants, provided it is not very long.'' Obviously the office will need filling before ``very long.''

     The president should fill it with Alan Greenspan. He has headed the Federal Reserve System under four presidents -- since August 1987. Now he is needed elsewhere.

     Historian Allan Nevins, Grover Cleveland's biographer, said Cleveland's problems ``never came as spies but as battalions.'' President Bush may soon know that feeling, partly because global economic winds will blow as they will, but mostly because of his ambitious agenda, particularly Social Security reform.

     Greenspan, a black hole of charisma, is, because of his reassuring lack of dash, precisely the person to embody sobriety in defense of bold changes, of which there soon will be many proposed. Greenspan, whose demeanor -- call it caution cubed -- does not suggest a man hurrying to Mardi Gras, has an unrivaled reservoir of credibility which can be drawn upon for five purposes:

     For preaching, as the Doha round of tariff reduction talks proceed, the rewards that flow from the discipline of free trade.

     For managing the decline of the dollar while reassuring financial markets that the decline is managed and healthy.

     For defending whatever tax reform the president proposes.

     For strengthening the forces -- if there still are any -- for spending restraint, moving the discussion beyond Vice President Cheney's pithy but, well, incomplete theory of public finance: ``Reagan proved deficits don't matter.''

     Above all, for defending Social Security reform against economic illiteracy and political demagoguery.

     The political difficulty with Social Security reform is related to two facts: No government program directly touches as many Americans as does Social Security, and none is more misunderstood. The term Social Security trust fund surely was designed to confuse -- to obscure the fact that the money paid in Social Security taxes does not prefund the future benefits of the particular taxpayers. That is, the Social Security trust fund is a financial obligation, not a financial asset. What Americans pay in payroll taxes -- roughly 80 percent of taxpayers pay more payroll taxes than income taxes -- provides benefits for current retirees, and the surplus of yearly outlays ($64.4 billion this year, but probably gone by 2018) buys Treasury bonds that will be redeemed when needed. Continued...