Some years ago in a moment of near whimsy, America's most intelligent liberal, Rep. Barney Frank, proposed the abolition of all political metaphors. Would we have gotten mired in Korea, he wondered, if we had not been convinced it really was "a dagger pointed at the heart of Japan"? How might history have been different if Korea had the shape of a plum?

In literature, metaphor makes for complexity, dimension and depth. In politics, it serves merely to simplify and thus distort. By far the worst offender is the medical metaphor. It deserves a special oblivion.

Politics is a realm of ambiguity and compromise. Medicine, on the other hand, is a world of black and white. A cancer, like all disease, is not only not human, but antihuman: malignant, invasive and murderous. It merits no quarter. The only relevant question when dealing with it is how best to destroy it.

Which is, of course, why polemicists love to depict their enemies as parasitic cancers, spreading infections, or boils fit only for lancing. An adversary -- even a member of an evil empire -- is entitled, by dint of his humanity, to certain feelings. Turn him into a cancer, and it becomes absurd to accord him rights or life or even pity.

The point of the medical metaphor is quite simply to dehumanize. Animal metaphors -- "fascist pig" -- have much the same effect (which is why Martin Peretz's New Republic, for example, forbids them even in cartoon drawings). Fascists, in fact, were the great specialists in both kinds of metaphor. They understood that once one's enemies are turned subhuman, the killing is easy.

Today the cancer metaphor is a favorite of the political right. The Sandinistas are not just a threat, but a cancer that needs cutting out. Similarly terrorism. The most famous use of this particular metaphor, however, came from Susan Sontag, who wrote in her more radical days that "the white race is the cancer of human history." (Some years later she repented of the metaphor -- not, mind you, because it was unflattering to whites, but because it was unflattering to cancer sufferers.)

Note that dermatological metaphors are distinctly unpopular. ("Stalinism spread like a rash across the face of Eastern Europe"?) Boils are the exception to this rule, because they call for a lance, which sounds martial. But anything that can be cured with a cream just won't do.

The medical metaphor often lends itself to ghoulish elaboration -- running sores, raging fevers, festering wounds. But these are mere flourishes. There are basically two kinds of medical metaphor: the metaphor of disease (cancer, infection), whose purpose is to dehumanize the bad guys, and the metaphor of healing, whose purpose is to sanctify the good guys.

Take the idea of the "surgical strike. " This is a military attack that kills only terrorists and leaves everything else, from innocents to French embassies, intact.

It is an index of how muddled our thinking about war has become that the surgical strike has become the only morally acceptable form of military action. (Incidentally, those metaphoricians who imagine surgery to be a synonym for cleanliness have never witnessed an operation.) President Reagan is partly to blame for this. For years now he has insisted, absurdly, that any attack that results in harm to civilians makes us terrorists too.

This is absurd because even in the strictest just war traditions there is an understanding that precision is not always possible. The question is not whether innocents may be "collaterally" injured, but what kind of objective justifies such an attack and at what risk. Not even de Vitoria or Suarez, the great late-medieval just war theorists, insisted that the use of force could only be just if purity were guaranteed.

Why the current popularity of the medical metaphor? It is more than linguistic fashion. It is a sign of low morale, of a loss of confidence in the justness of our own causes and of the exceedingly restrained means we have chosen to pursue them in the world. (The sum total of American military actions in the last 10 years would hardly add up to one afternoon's violence in a brushfire war.) We can only bring ourselves to take military action under cover of white coats and under the pretense that the job is not war but hygiene.

We are ready to fight only cancers and then only "surgically." Why? Because it has become too difficult to fight real enemies whose humanity we can respect but, at the same time, whose purposes we know we must defeat.

Enough. Enemies are not cancers. War is not surgery. And international politics is not medicine. If it were, we should disarm. After all, the ultimate Hippocratic rule is "first, do no harm." A rather confusing order to give the pilot of an F-111.