John Foster Dulles had a way of putting even sensible things controversially, as when he proclaimed in a 1956 interview in Life magazine that "the ability to get to the verge without getting into war is the necessary art. If you cannot master it, you inevitably get into war--if you are scared to go to the brink, you are lost."

Adlai Stevenson and the Democrats quickly coined the buzzword "brinkmanship" and translated it into a willingness to engage in reckless bluffs. But in fairness, Dulles was only trying to get a handle on strategy as old as gunboat diplomacy and as new as the Falklands conflict: the threat of the use of force in a big and decisive way (sometimes by using it in a selective way) in an effort to achieve a diplomatic settlement or to deter an aggressive act.

Comes now the latest practitioner, British Prime Minister Margaret Thatcher, with a very heavy hand. By blockading the Falklands, bombing airstrips, sinking warships, and threatening large-scale troop landings, the British are edging right up to what, for them, would constitute the "brink."

That would be the point just before a direct, all-out assault on East Falkland Island-- the one where almost all the British inhabitants are--and a head-on clash with its Argentine occupiers. That operation, unlike a landing on the lightly defended western island, would risk a heavy British loss of life.

Nobody (save, perhaps, a few members of the Labor Party opposition on the far left) has so far been tasteless enough to call this "brinkmanship." But the Dulles doctrine, as he enunciated it in 1956, nicely defines the dilemma confronting the British in May of 1982. It also raises serious questions about Britain's ability to master "the necessary art."

This is not to knock the skill or the rightness of the British effort. It is merely to invite consideration of the considerable risks and uncertainties inherent in a strategy that turns as much on states of minds and political will as it does on firepower, military technology, morale and the capacity to deal with the particular physical conditions at hand.

The last are difficult enough to weigh, as you will doubtless have gathered from the sheer volume of military analysis: the performance ratings of ships, aircraft and troops on both sides. So far, the British have succeeded in a strictly military way, accomplishing carefully calibrated missions with a minimum of British--as distinct from Argentine--bloodshed.

But brinkmanship, in the best sense, is not a function of firepower alone. It has to do with each side's perceptions of the other, which is to say with essentially unknowables and unpredictables. It is not enough to "get to the brink." The mind-numbing nature of this business is that in order for it to succeed, the practitioner has to demonstrate convincingly a willingness to see it fail.

Now this would be one thing--and quite difficult enough--if Argentina's military dictatorship were Britain's only audience. But the sort of things the Thatcher government must say, and do, by way of chastening the junta in Buenos Aires are heard, and heard about, in Britain as well. And while the military feats may be heady stuff, earning Thatcher rising ratings in the polls, they plainly are not expected by the British public to result in the loss of British lives. The most recent sampling of British opinion shows 70 percent of the people "satisfied" with Thatcher policy. But about the same considerable majority does not think the Falklands are worth the shedding of British blood. The tactics so far employed by British forces suggest a keen awareness of this public sentiment.

Thatcher, in short, must necessarily strike a careful balance between the right combination of military pressure calculated to crack the will of the Argentines and a level of military action (and casualties) that is tolerable at home. Calculating the state of mind of the Argentine leadership is hard enough; calculating the Argentine leadership's calculation of the collective British state of mind introduces yet one more excruciating uncertainty.

When you add the worsening weather, which argues for a quick and conclusive turning of the military screws, to the need for a certain military prudence, which argues for caution, you have compounded the already considerable complexities of "the necessary art."

Before loss of the destroyer Sheffield and the Harrier jet the British were comfortably ahead on points--though the sinking of the General Belgrano with hundreds of casualties may be giving even Britain's best friends some pause. But this conflict combines psychological warfare with calculated whiffs of e real thing. It turns heavily on the unpredictable play of internal politics. It is not, accordingly, an easy one for bystanders to score.