WHEN I READ about the "historic" treaty and the great debate called SALT, it reminds me of those ruined castles along the Rhine and I smile. One is entitled to smile at history's follies or quake, whichever suits your temperament.

I first saw those medieval castles on a boat tour a few years ago, the classic tourist cruise up the Rhine. At first, I was overwhelmed by the romatic dread which these ruins evoke, towers and ramparts crumbling peacably on the gree hills along that great river. The Rhine has dozens of castles, most of them built 500 years ago when Europe was a patchwork of contesting dukes and a patchwork of contesting dukes and barons and tow-bit kings, before there were full-grown nations as we know them.

After so many castles, the romanticism wears thin and we gross Americans began to laugh. The guidebook told us in sober detail how each castles.

And how each castle was destroyed. Overrum, sacked, burned, dismantled by a c onquering army. Wars were begining to adopt new waponry based on the latest technology, gunpowder.

Nevertheless, the dukes kept buildong new castle -- long after it was evident that castles no longer povided security or power. I can imagine the hapless peasants and yeoment toting all those heavy rocks up the hill, shaking their heads grimly.

Why are we building this castle anyway? Because the duke says this castle is a "war-winning" castle much better than the old castle. The duke was wrong, again and again, bt it took 200 years or so before people could grasp that warfare had changed fundamentally, that power now required nation-states with defensible borders and industrial capacity and large supplies of cannon fodder.

Rougly speaking, I thing this is where the world is today, at a similar watershed. We are confronted by new realities, but great antions proceed to plan war as though nothing has changed. The world's superleaders, whether we call them hawks or doves, whether they are in Washington or Moscow, plot nuclear war strategies in the old terms because, like the medieval dudes, they are unwilling t believe that the fundmentals have changed. This is a perfectly natural human habit, imposing the obsolete past on a different future, but dangerous.

The rest of us, therefore, are reduced to the role of hapless peasants, paying our taxes and shaking our heads. It looks crazy to me, these new "castles" tha Jummy Carter and his Urssian adversary intend to build, but I figure the world must learn the new realities the hard way, incinerating many human beings in the search for a new theory of war.

Perhaps my ruined castles on the Rhine seem too romote to serve as a believable metaphor, but another peach-making chapter lies much coser to the "Strategic Arms Limitations" treaties of our own time. After World War I, the supepowers agreed that modern war was dreadful. At the battle of the Somme, 60,000 British died in a few days, marching like lemmings into German machine-gun fire. Nobody wrote songs about that. After World War I, the great powers held three disarmanent conferences and each produced an arms-control agreement which was hailed as "historic" in world capitals, including Washington.

Warld War II followed shortly thereafter. It was more dreadful than anyone could have imagined in 1978. In the romatic legend of warfare, it was once regarded as beastly, even criminal, to bombard civilian populations. Armies were supposed to fight on battlefields and respect the lives of noncombatants caught in te crossfire. In World War II, civiliam populations. Armies were supposed to fight on battlefields and respect the lives of noncombatants caught in the corssfire. In War II, civiliam populations became the strategic targets of global combat, from London to Dresden to Hiroshima.

A lot of today y's strategic double-talk from the nuclear thinkers pretends that civilians will not be targets in the next big one.Here is one hapless peasant who doesn't believe them.

Today, one of the most dangerous illusions afloat in American opinion is that nuclear war is "unthinkable." Politicians encourage this notion, knowing that it will comfort us. But, as I read history, there are very few instances when warrior nations voluntarily gave up the use of new technology, as long as they thought the new weapons were effective. If nuclear war is "unthinkable," why do so many experts, in and out of government, in Washington and in Moscow, spend so much time thinking about how to do it?

Our century of megadeaths now sustains a nuclear intellecutal-in- dustry, the rewards are obvious. For the inintelluectuals, the subject must seem like a heady game of global chess, with Minneapolis and Vladivostock as pawns,s, Houston and Stalingrad as rooks, Washington and Mo oscow as kings or queens. One of my favorite chess strategies is the "war-winning" scenario devised by Paul Nitze in which the victor only loses 10 or 20 million lives. What a noble work is man.

The SALT debate evokes, for some of us, a renewed sense of nuclear dread. Not romantic poetry or martial music. Some of us are not yet sufficiently adjusted to the concept of megadeaths to see any romanticism in those old photos of Hiroshima, where every brick and stone was leveled, when the deformed survivors waited patiently to fie of radiation poisoning.

I have been urged to find reassurance in the "SALTProcess," as it is called in this town [there is something ludicrous in the name alone, if you think about it]. I am familiar with the arms control theology but I do not find the results reassuring. If one putd aside theories and hopes and examines only the concrete results, the SALT process looks quite dangerous to me, dangerous because it convinces unattentive citizens that somebody is doing something to control the nukes.

I don't see much control, In the early 1970s, when the United States first began to talk about arms agreements with the Russians, we had about 400 nuclear warheads -- enought to obliterate the Soviet Union, people, factories, trees, dogs and bears. By 1972, when SALT I was signed, we had 3,000 warheads. Now in 1979, when SALT II is signed, we have nearly 9,000 warheads. by 1985, when perhaps the diplomats will deliver SALT III, the United States intends to have 16,000 to 18,000 warheads.

Wishful optimists may call this "arms limitation" if they wish, but it should not deceive the rest of us. I doubt that many Americans realize that the American arswnal will grow from a few hundred nukes to 18,000 under the aegis of arms control. My own belief is that the majority of Americans would be horrified, also scared, if they did understand. The Soviet arsenal, of course, has grown even more dramatically because the Reds were playing catch-up.

Our hawks look at what their hawks are doing and find a dozen new reasons why we are still "weak" and, therefore, must build every new elaboration which technology invents -- long, massive trenches in the West where we can hide out rockets on subterranean railroad cars, a new generation of gargantuan missiles like the ones Russia has built. Soviet hawks will doubtless sell similar arguments and the Reds will biold highly accurate missiles like ours. This is not a transendantal process; it is more like a wheel, on which small, furry animals follwo each other's tail.

Mabye the great debate will change my mind, but I am not conviced that these arms treaties have much lasting meaning. When I say this to true belivers, they urge me to be patient. Wait until the next treaty. It will really accomplish something. But this is what they said after SALT I. SALT II is the "next treaty" and it is as weak as the last one. Its main value seems to be comfort for the our modern muddled dyjes abd barons, assuring them that they are indeed in charge of history.

It seems crazy to me and I use that inflammatory word deliberately. If madness is the condition of behaving in accordance with a false sense of reality, then the arms race is surely guided by a kind of collective madness, in which leaders of both camps respond to the obsolet past, not to the menacing present

If the SALT process collapses, that will create a terrible political trauma but it might also awaken the peasants to a new conciousness of where we truly are in the nuclear age. This new conciousness is now feeble and unformed, but alive and amerging.

For me, the only interesting question is this: Will the new consciousness gain strength and take hold of human events before the old consciousness gets us all killed?