THE SHULTZ-GROMYKO talks in Geneva were a revealing extravaganza. The hoopla, the ridiculous media overkill (nearly 500 accredited American journalists!), the enormous ado about a procedural diplomatic event that did nothing but get us back to the same negotiating table with the Russians -- all this was a sign, if another were needed, that we've lost touch with the basic realities of nuclear arms and arms control.

Why did we get so lathered up about the Geneva meetings? Perhaps because they spoke to some primal anxiety about nuclear weapons. But also because of the delusion that somehow, after five years of inaction in arms control, one meeting was going to make a profound difference in the Soviet-American relationship.

It is conventional wisdom in Washington these days that if he really wants one, Ronald Reagan is bound to be able to get an arms control agreement in the next couple of years. But this conventional wisdom is not shared by many of the people who worked on SALT I and II -- people who know what really goes into negotiating one of these deals.

The SALT I treaty required three years of intense negotiations involving the senior officials of both governments. The SALT II treaty took six years to complete -- the weaponry and the politics were both getting more complex. But no real progress has been made on the next arms control agreement, and the issues have gotten still more complicated.

In fact, the Reagan administration has no conceptual idea of what kind of deal it wants, or how it might persuade the Russians to move in the same direction; it earnestly seeks to protect all American advantages and new programs, while forcing the Soviets to abandon many of theirs. This is not a formula for success.

The idea that this administration is now on the road to a new agreement with the Russians is one of the myths that clouds discussion of these matters. It's tempting to argue that the myths outnumber and outweigh the facts. Consider a few of them:

The Soviet buildup. The president and his secretary of defense have been telling us emphatically for four years about the relentless Soviet arms buildup. Several years ago they were saying it had actually given the Russians a clear strategic advantage.

Reagan and Weinberger have demonstrated once again that any allegation of this kind, repeated often enough from authoritative quarters, becomes an accepted fact. Who now doubts that the Soviet Union has indeed engaged in a relentless buildup, one that has intensified since the SALT I and II treaties were signed?

Well, anyone who reads the inaugural issue of a new academic journal called Soviet Economics will have to doubt that wisdom. Using already-released (but little discussed) CIA estimates, Richard E. Kaufman of Congress's Joint Economic Committee explains in a detailed artile in the journal that the very real Soviet buildup of the '60s and '70s actually slowed down significantly after 1976.

From 1977 to 1981, according to the CIA, Soviet procurement of new weapons measured in dollars (that is, calculated to show their cost if the U.S. had acquired the same weapons) did not grow at all. This pattern probably continued in 1982; more recent figures are not yet available.

The CIA's numbers show that Soviet spending on armaments slowed down markedly in the mid- '70s. For the previous decade it had grown at constant rates of nearly 5 percent a year; in the last decade the growth has been 2 percent a year (much less than the growth of American spending).

In other words, during a decade that President Reagan has described as a period of relentless Soviet buildup, the Russians actually cut the growth of their "defense spending" by more than half! How can we conduct a serious discussion of these issues when the facts and the rhetoric are as discordant as that?

The Strategic Defense Initiative, or "Star Wars." Any concerned citizen reading the papers knows that the Russians are alarmed by the American "Star Wars" program, intended, in one of President Reagan's memorable phrases, as "a means of rendering these nuclear weapons impotent and obsolete."

Reagan introduced this idea in March 1983, and since then it has taken on a life of its own -- become so real that a reporter could ask the president at his news conference last week if he would "consider setting limits on the deployment and the testing of 'Star Wars?'".

In fact, there is no 'Star Wars' system to test or deploy. The idea remains a dream. In its extreme form, as a scheme to render nukes "impotent and obsolete," it is a pipe dream. No responsible scientist could suggest that such a goal is feasible with any known technology.

Someone on the president's staff seems to have gotten through to him with this reality. The White House released a pamphlet designed to promote the Strategic Defense Initiative (SDI) earlier this month; in a forward signed by Reagan, the SDI was redescribed as a means of "rendering ballistic missiles (not all "nuclear weapons," as he said in '83) impotent and obsolete." Even if that were possible (and in the forseeable future it isn't), bombs could still be delivered by airplanes, unpiloted drones called cruise missiles -- or by terrorists carrying them in suitcases. Is any Congress going to appropriate the hundreds of billions -- some experts say at least a trillion dollars -- that a Star Wars program would cost if it only holds out the problematic hope of disarming some Soviet missiles, but not protecting against nuclear bombs delivered by other means?

The "Star Wars" myth has a cynical aspect that deserves more attention than it has received. The president's grandiose idea has undeniable popular appeal; who wouldn't like to think we can find a foolproof defense against nukes? "All through history we've been able to come up with a defensive weapon," the president likes to say -- why not with these weapons, as with all others? (But wait: what "weapon" did we invent to defend against the bullet? Against germ warfare? No, Reagan is wrong about that, too.)

The appeal comes from the thought that defense is possible -- that we might avoid nuclear holocaust through technological ingenuity. This, the president says, would allow us to escape today's "immoral" reliance on deterrence -- the threat of a devastating retaliatory attack if the Soviets attacked us -- as our only defense against nuclear war.

But Reagan administration officials responsible for Star Wars recognize -- and have publicly acknowledged -- that until unforseeable technical breakthroughs are achieved, all we can hope for is a defensive system that might offer protection for some of our own land-based intercontinental ballistic missiles. These officials, including George Keyworth, Reagan's science advisor, say we could build a defense that would knock a lot of Soviet missiles out of the sky before they could destroy our missiles in their silos.

What would be the good of this? Why, it would "enhance deterrence" -- that is, it would increase the possibility that even if the Russians attacked us with a huge first strike, some of our missiles would survive, and would be able to attack the Soviet Union, destroying it as a functioning modern society. What happened to Reagan's noble idea of evading the immorality of deterrence? Up in smoke. In the name of going beyond deterrence, Star Wars becomes a program to reinforce it -- at enormous cost, and in a way that would inevitably compel the Soviets to build more offensive weapons. (How else could they counter a new American system that could destroy a portion of Soviet rockets in flight? They would build more rockets, and more decoys too.)

Soviet indifference to nuclear dangers. How many times have you heard that the Russians just don't believe in the doctrine of deterrence, or "mutual assured destruction"? This is now a commonplace among many experts and commentators: the United States, it is said, might accept the idea that launching an attack is crazy, because we'd be destroyed by the Soviet retaliation; but the Russians somehow don't agree, and believe they could survive and win a nuclear war.

The traditional American view of deterrence is based on thoughts like these: "With the quantity and diversity of nuclear missiles that already exists, it is impossible to destroy the enemy's systems with a single strike. A crushing retaliatory strike against the aggressor, even by the limited quantity of nuclear weapons remaining to the defender -- a strike inflicting unacceptable damage -- is inevitable in present conditions." Many believers in the effectiveness of deterrence would agree that "you don't have to be a military man or a scientist to realize that a further buildup (of nuclear weapons) is becoming senseless." To hear the hard-line commentators tell it, though, the Russians won't buy those notions.

Those two quotations, however, come from Marshal Nikolai Ogarkov, until September the chief of the Soviet general staff. He made those remarks in an interview with Red Star, the newspaper of the Soviet Defense Ministry -- the medium through which Soviet military men learn the party line.

The failure of past arms control agreements. If you read or watched the outpouring of media pronouncements last week, you were told repeatedly that SALT I and II and other arms control agreements failed to slow the arms race -- that it went on virtually unabated despite those pieces of paper.

This is another of those oft-repeated truths that is wrong. Thanks to past agreements, no nuclear weapons are tested in the atmosphere. Neither country can try to deploy an effective defensive system, so neither can seriously dream of launching an attack that would result in anything but its own destruction. Both sides are required to limit their arsenals to fixed numbers of offensive missiles and warheads. (These limits are high, but they do prevent a wild new arms race; if such limits are not in force, no Star Wars system is likely to be effective even against Soviet rockets, because the Soviets will build too many.) Thanks to SALT II, both sides have agreed on "counting rules" that would enable them to verify new agreements substantially reducing the number of deployed weapons; without such rules, future agreements will be impossible.

This is only a partial list of the many benefits of earlier arms control. The Reagan administration confirms that these benefits are real by continuing to adhere to all past agreements, even the SALT II treaty that it publicly deplores.

It's also said that the Soviets routinely exploit every arms control agreement to the hilt, pushing each provision to its limit if not beyond. But as John Steinbruner of the Brookings Institution has pointed out, SALT II would allow the Soviets to have nearly twice as many warheads on their missiles as they actually had as of mid-1984; they're far below the permitted maximum.

At the same time, in his first term President Reagan demonstrated convincingly how the arms race can be reinvigorated without arms control. He has opened the door to new and expensive competitions in anti-satellite weapons, weapons in space, cruise missiles and more.

Future historians, if there are any, will probably look back at these first four decades of the nuclear era as a time of self-delusion and struggle -- struggle to come to terms with the facts of thermonuclear life.

So far the struggle has gotten the best of us. Aware from Hiroshima onward that we were dealing with a new kind of monster, we have tried to tame it, to master it. These efforts have led us to a world of 50,000 warheads and delivery systems of a sophistication that was unimaginable 40 years ago. In many practical ways we see that military men and politicians realize that these weapons are unusable, yet we keep building more of them. In sum, we have confirmed the genius of Albert Einstein's insight that "the unleashed power of the atom has changed everything except our way of thinking."