We have set back diplomacy by 500 years. Prior to the 15th century, kings and princes did business with one another by elaborate personal visits and then by special envoys. But in 1455, an Italian city-state first established a permanent diplomatic mission in a foreign sovereignty and that practice was soon universally adopted. American diplomacy has now reverted to the pre-15th-century pattern.

Consider our current application of these medieval arrangements. We use our embassies as observation posts, while reducing our ambassadors to messengers boys. All important business is transacted by direct visits of the president or the secretary of state or even of that aberrant diplomatic mutation, the national security adviser. Lately we have resorted to highly publicized missions by American personalities primarily known for their prowess in other fields. Accompanying those dignitaries is a restless retinue of press and television reporters to record their between-innings banalities enlivened with the informal indiscretions of an anonymous "official on the plane." All that provides rich fodder for the afternoon news shows, but it seriously impedes the conduct of a coherent foreign policy.

Secretary of State John Foster Dulles was the first to exploit the "do-it-yourself" potential offered by Air Force One and its siblings, while Henry Kissinger seems never to have understood any other methods. But, unhappily, the addiction did not stop there. A reversion to an ancient diplomatic procedure that began as an expression of two hypertrophied egos is being perpetuated by a more modest successor, who has even made a pilgrimage to the terrorist leaders of the Zimbabwe Patriotic Front. Meanwhile, restricted by the episodic limitations implicit in this method, our government has repeatedly overlooked deteriorating relations with countries not in the immediate spotlight, while permitting dangerous situations to develop without timely or adequate attention.

The prospects for drift and breakage inherent in these atavistic diplomatic procedures were intensified when Kissinger's impressive theatrical flair transmuted his virtuoso diplomacy into something novel and seductive: Diplomacy as Showbiz. During his spectacular season on state, his attempt to bring two nations into agreement became an enthralling dramtic event, with the secretary of state pitting his skills (and America's pocketbook) against an Israeli and Egyptian bargaining power that was progressively inflated by the process. Thus the world was wonderfully entertained by America's "miracle worker" flying like Superman between Middle Eastern capitals, while press and television breathlessly reported, "He's down; he's up, he's gaining momentum!" and political commentators sounded like sportscasters.

Showbiz diplomacy has notable limitations. It destroys the scope for quiet and subtle maneuver available to a less flamboyant approach, such as that habitually practiced by the most skillful American negotiator of modern times. Ellsworth Bunker, who repeatedly achieved prodigious feats of mediation at almost no expense to the American taxpayer by never letting his own ego become a factor in the bargain. But an even more important defect of the method is that it narrows the goal of the contest to the conclusion of the agreement -- almost any agreement -- without sufficient regard for its cost or content. Kissinger's most theatrical achievement, Sinai II, was for example, an unprecedented real-estate transaction in which the United States paid Israel an exorbitant price, both in money and political commitments, for a huge acreage of desert said and a few oil wells that it then paid the Egyptians to take over.

The Camp David Accords -- which might properly be called "The Son of Sinai II" or, more sucinctly, "Sinai III" -- expanded that transaction to include the balance of the desert with additional huge payments to each side. Of course, that was not all President Carter intended; he had initially set out in great good faith to produce a comprehensive Middle Eastern agreement that would go to the heart of the dispute -- the settlement of the Palestinian issue. But, here again, the pressures of a theatrical diplomatic process constricted the focus to the narrow objective of getting both sides to sign something -- an objective of getting both sides to sign something -- an objective that became all important when the president engaged his personal prestige in the effort. The agreement that emerged has, by polarizing the Arab world, prejudiced any ultimate solution of the festering, substantive problems of the Arab-Israeli dispute to the disadvantage of the United States.

Recently we have witnessed a further variant of Diplomacy as Showbiz: the Prima Donna as Diplomat. Those two well-publicized personalities, Ambassadors Andrew Young and Robert Strauss, have both shown their disdain for the accepted rules of diplomacy. Young put the cap to a long career of free-wheeling by talking against intructions to a PLO representative, while Strauss returned from a mission to the Middle East with the announcement -- unprecedented in diplomatic history for a serving ambassador -- that he had never believed in the mission on which he had been engaged and was unprepared to accept instructions from the secretary of state.

It is not surprising that the chancelleries of the world have reacted to all this with a nervous mix of belly laughter and disbelief. No doubt, if we continue to practice our modern version of medieval diplomacy as showbiz, replete with well-advertised stars addicted to improvisation, while our permanent diplomatic establishment atrophies from desuetude, we can made foreign policy more entertaining. But at what cost to American leadership? Even if it's less fun, shouldn't we once again move boldly forward to the 15th century?