Remember the film "Butch Cassidy and the Sundance Kid," when Butch and Sundance are failing to elude a posse? Butch constantly looks back, saying "Who are those guys -- they're really good!" We who write in Washington felt that way when Charles Krauthammer first appeared in our midst as a columnist. We knew how baseball's lesser pitchers -- which means all other pitchers -- felt when they first glimpsed Dwight Gooden. They thought: He is unreasonably good and it is unreasonable to doubt that he will get even better.

Already Krauthammer is a one-man saving remnant of the Democratic Party's vanishing middle. And his MIRVed mind contains enough arguments to demolish the hardened assumptions in an entire federal department (State).

President Reagan's bedside table is, I am sure, groaning beneath riefing books bulging with (I suspect) unreadable and (I pray) unread State Department papers. Better he should curl up with the first five pages in Krauthammer's new collection of essays, "Cutting Edges." They concern the "mirror image fallacy," the cheerful belief that the whole world is "like us."

Solipsism, the belief that the whole world is me, is a mental illness. What Krauthammer calls "plural solipsism," the belief that the whole world is like us, is a principle of U.S. diplomacy. As a doctor on one of those "physicians against war" outfits puts it, Russian and American hearts are indistinguishable and thus all ache equally for peace. It is, he says, "a simple medical insight."

Plural solipsism teaches that because we are all alike in our values and desires, conflicts must be explicable as failures to "communicate." This is, Krauthammer says, "the broken-telephone theory of international conflict." If we are all alike, horrid thoughts and vicious plans must be passing aberrations. So, "the more alien the sentiment, the less seriously it is taken." For example: We will bury you.

When democracies, with their bland imaginations, deal with totalitarians, the result is incomprehension. As Krauthammer says, "When the comfortable encounter the unimaginable, the result is not only emotional but cognitive refusal."

Krauthammer rejects today's fashionable agnosticism about the Cold War, and also the various isolationisms. In 1984 the great Central America debate between Hart and Mondale (for whom Krauthammer once wrote speeches) concerned whether there should be 20 (Mondale) or zero (Hart) U.S. advisers in Honduras. Watching this, Krauthammer decided that a new form of isolationism is internationalist in aims but isolationist in means. It holds that the United States should confound its enemies with processes: the Mideast peace "process," the arms control "process," the Helsinki "process," the Contadora "process."

U.S. policy should be to "care," and "express" ample "concern," but for God's sake do not send troops to rescue Grenada from Stalinists. However, as Krauthammer says, to renounce force and rely on passive foreign- policy instruments -- exhortations, primarily -- is to decide to act only against flawed friends (El Salvador, the Philippines, South Africa, South Korea, Chile, Taiwan).

In lamenting the eclipse of America's political center, Krauthammer begins at the beginning. The Constitution's preamble requires the government to look after the common defense and the general welfare. So government needs a big heart at home and a strong hand abroad. But today "the two parties have neatly divvied up these responsibilities between them, Republicans committed to defense ('strength'), Democrats to welfare ('fairness')." Regarding defense, Democrats specialize in impotent denunciations. Regarding welfare, Republicans speak, ambivalently, of safety nets, "the language of rescue teams and circuses."

Krauthammer says that since the death of Henry Jackson he has felt like a political orphan. He has more than a few siblings.

Dwight Gooden's nickname is "Dr. K" -- "K" being the baseball symbol for a strikeout. Like Gooden, Washington's "Dr. K" plays a game of inches -- of precision: "Why, after all, say 'single-parent family' when we mean fatherless home? (Single, male-headed households are a small minority of the single-parent family group.) The descriptive, and sympathetic, 'fatherless' acknowledges that something is missing; the ostentatiously neutral 'single- parent family' would have us believe that the distinction between a single and a double -- why not a triple? -- parent household is entirely statistical."

After studying political philosophy at Oxford, Krauthammer, who now is all of 35, got a medical degree at Harvard. From medicine he acquired scientific literacy. From doctoring he learned to distinguish real suffering from "the more literary forms of anguish." From Scoop Jackson's steady example he learned the art of, well, steadiness. Dr. Krauthammer's Jacksonian persuasion is just what the doctor ordered for the Democrats.