It has finally happened. Arthur Schlesinger Jr., of all people, has paired "Keynesianism" with "Lafferism" as failed economic doctrines. "The favored economic models no longer work," declared the historian in a recent Wall Street Journal commentary. "Keynesianism, the offspring of depression, never had a clear line on inflation. Lafferism lacked an analytical base and is today in ruins."

Schlesinger's prose is seductively smooth. So this indigestible lump probably slid down the whistles of his Journal readers without causing so much as a hiccup. It is polite understatement to say of "Lafferism," so named for Arthur Laffer, the Southern California economist and godfather of Reaganomics, that it lacks an analytical base. The celebrated "Laffer curve," which purports to show that Draconian taxation kills economic incentive, embodies a truism. Somewhere short of 100 percent, there is undoubtedly a rate of "marginal" taxation that would drive a sane earner to idleness or furtive barter. But as a guide to policy in a modern industrial economy, Lafferism is inadequate.

This is hardly true today of Keynesianism. In some forms, Keynesianism (especially as construed by its detractors) would be as unrecognizable to John Maynard Keynes as most Marxism would be to Marx. In popular parlance, Keynesianism seems to mean a free-spending economic doctrine and little else. Keynes published his revolutionary theoretical work, "The General Theory of Employment, Money and Interest," in 1936. Then, there seemed no escape from chronic mass unemployment. The economic wise men of his time imagined that there existed a natural economic "equilibrium" ordained by God Himself at full employment, if only governments would not meddle with the markets. Keynes' shocking message was that God helps economies that help themselves.

Within 20 years of the publication of "The General Theory," most governments accepted the need for vigorous intervention to regulate the business cycle and promote full employment. But the recent surge of hyper-inflation, when governments failed to tax enough to pay for a lengthening list of services, nourished a false belief. It was that Keynes, the great doctor of depression, had no medicine for price instability; indeed, that he was indifferent to it. As any inclusive sampler of his writings shows, Keynes was anti- inflation to the marrow. "There is," he wrote, "no subtler, surer means of overturning the existing basis of society than to debauch the currency."

Most governments tend to be half Keynesian. They stoke the economic engine when recession hits. That is basic Keynesianism. But they fail to achieve the budget balances and surpluses that would soak up excess demand when economies overheat. That is not Keynesian.

The failure is more political than economic, as the case of Ronald Reagan shows. The president, long a scourge of deficit spending, has lately described the mega-deficits induced by deep tax cutting as "necessary evils." He is half right: they are evil. Keynes taught governments to weigh hard alternatives. Reagan wants it all--a balanced budget, big rearmament, jobs, price stability. But those goals clash in the real world, and Reagan seems inclined to jettison fiscal solvency first. Ironically, the predictable consequences of the high-deficit course will further reinforce the notion that Keynesianism has no line on inflation and is out of date. It isn't. It is simply ignored.