On THE EVE OF nuclear arms talks in Geneva, the Reagan administration is bending itself into knots trying to pretend that it has a coherent national security policy that could produce both an American "Star Wars" defense and a sweeping arms control agreement with the Soviet Union.

There are two possible explanations for the administration's gyrations. One -- the most hopeful, but also the most unlikely -- is that we are witnessing a surpassingly shrewd bargaining operation by a group of master poker players, who are maneuvering the Russians into historic negotiations that could actually reverse the arms race.

The second and more likely explanation is that we have entered a strategic Wonderland, guided by a president obsessed by a doubtful idea, who is advised by "experts" whose principal expertise is concocting "rationales that don't torture the facts too badly," as a Republican Senate aide put it last week.

President Reagan's idea that we can have Star Wars and negotiated disarmament, too, is considered implausible by nearly everyone who follows these issues closely from a vantage point anywhere outside the Reagan administration. Superhawks on Capitol Hill, arms controllers, experts and officials all over Western Europe, senior members of past administrations -- and numerous officials in the present American government who are never heard from in public -- consider this an unrealistic approach.

Why? Because it would require the technologically inferior Russians to accept an entirely new and staggeringly expensive competition to build defensive weapons -- not just another weapons system, but the biggest, boldest, most complex technological enterprise ever undertaken by the human race. At the same time, the Soviets would have to accept the elimination of a large fraction of their offensive weapons despite the fact that, if America succeeds in building a defensive system, deploying large numbers of offensive weapons will be the easiest way to counter its impact. (In other words, we're telling the Russians, there's about to be a famine, so please throw out all the canned food in your basement.)

Why should this proposition appeal to the Russians, who struggled so long to match or surpass the United States in most existing strategic weaponry, and now face a grave economic crisis in their own country? Here's an answer to that question offered by Lt. Gen. James A. Abrahamson, the Pentagon officer in charge of strategic defense:

"Remember that the Russians are afraid of our technology. That is what all this business is about. When they see that we have embarked on a long-term effort to achieve an extremely effective defense, supported by a strong national will, then they will give up on the development of more offensive missiles and move in the same direction."

One quivers at the thought that Gen. Abrahamson may have grandchildren who might be asked some day to answer for that assertion. The Russians are going to give up on the offensive weapons they rely on for their security? Like docile pussycats, they are going to fall into line behind us rather than find ways to counter what we do?

Paul Nitze, now the coordinator of administration arms control policy, who has had much more experience dealing with Russians than Gen. Abrahamson, answers the question in vaguer terms. Here's how he put it recently: " . . . We hope the Soviets will come to see the merits of our position -- that it will serve their national interests as well as ours."

But they won't see that, because it won't ever be true. The Star Wars program described blithely by the president and his men (well, some of his men) as a benefit to both superpowers is in fact an ominous threat to whichever of them fails to get it first, because it would give its owner an enormous potential advantage in a war.

Don't take a journalist's word for it, just listen to Caspar W. Weinberger: "It takes very little imagination to realize what a vastly more dangerous world this would be if they (the Soviets) attained this ability to destroy our missiles, and we did not have a similar capability." Or Weinberger on another occasion: "If the Soviets get strategic defense and we don't, it would be very much like the world in which the Soviets had a nuclear weapon and we did not."

In other words, according to President Reagan's secretary of defense, for one superpower to have a functioning missile defense when the other did not would leave the other at a desperate disadvantage. Yet the United States proposes to build its defense first, and brags that the Soviets will have a hard time matching its technology.

The Russians have noticed this contradiction. Col. Gen. Nikolai F. Chervov, a senior official of the Soviet general staff responsible for arms control issues, actually quoted that second Weinberger statement to reporters in Washington last week. Chervov had memorized it.

Consider the Reagan administration's road map pointing the way from here to the ideal world of mutual missile defense. These four sentences, introduced and often repeated by Nitze, are called "the strategic concept" at the heart of administration policy. Read them carefully:

"During the next 10 years, the U.S. objective is a radical reduction in the power of existing and planned offensive nuclear arms, as well as the stabilization of the relationship between offensive and defensive nuclear arms, whether on earth or in space. We are even now looking forward to a period of transition to a more stable world, with greatly reduced levels of nuclear arms and an enhanced ability to deter war based upon an increasing contribution of non-nuclear defenses against offensive nuclear arms. This period of transition could lead to the eventual elimination of all nuclear arms, both offensive and defensive. A world free of nuclear arms is an ultimate objective to which we, the Soviet Union, and all other nations can agree."

Got it? No, probably not, because there is almost nothing there to get. You don't need a Ph.D. in nuclear strategy to understand that this "strategic concept" contains neither a concept nor a strategy, but merely a wish.

And a wish of the most dubious sincerity, too. In order to achieve a "radical reduction" and a "stabilization" of nuclear forces, the Reagan administration is already building a dizzying array of new, often destabilizing weapons. This buildup has nothing to do with Star Wars, which would come later.

For example, we are now just a few years away from deployment of the super-accurate "D-5 missile" that will carry eight individually-targetable nuclear weapons, and will sail beneath the world'sn Trident submarines. The MX missile gets all the publicity, but the D-5 is a considerably more important departure for the United States. It will give us an "invulnerable" (because hideable at sea) capability to wipe out Soviet missiles in their silos (because the D-5 will be so accurate), something neither side has had before.

The existence of large numbers of D-5 missiles threatening the entire Soviet land-based missile force would put enormous new strain on the stability of the nuclear balance in a crisis. (Knowing that their principal attack forces might be wiped out by D-5s, the Russians would always be tempted to use their rockets rather than lose them.) But that's what we're in for. Of course it's far from all that we're in for. We are also building new B-1 and "stealth" bombers (the Stealth is meant to be nearly invisible to Soviet radar), 760 new nuclear cruise missiles for deployment on ships at sea, about 3000 more cruise missiles to be carried by aircraft, 464 to be based on land, new Pershing II ballistic missiles for deployment in Europe, etc. Shall we now conclude that the promise of "radical reductions" and "stabilization" is more significant than this hardware, which is right now under construction?

The Reagan administration is arguing that the best way to get deep cuts in the superpowers' nuclear arsenals leading to a world without nukes is to complete a major buildup of offensive weapons, then begin a huge new defensive arms race. This sort of reasoning is not based on secret information or expert knowledge about the esoterica of nuclear strategy. We're squarely in the realm of common sense. What do you think is the best way to push the superpowers toward lower levels of strategic weapons? By building many, many more? Or by starting now, at current levels, to negotiate reductions?

The essence of the Star Wars idea is easy to grasp. It is not a path to guaranteed protection from nukes -- even its strongest proponents acknowledge that fabulous new technological breakthroughs will be required to make it work. It is not an end to what Reagan has called the "immoral" reliance on the mutual guarantee of nuclear destruction as the principal deterrent to nuclear war. Reagan's closest aides have said repeatedly that we will continue to rely on deterrence -- that is, on that "immoral" balance of terror -- even if we get Star Wars.

No, the essence of Star Wars is the promise of a fabulous new bonanza for what President Dwight D. Eisenhower called the "military- industrial complex." All that is certain if we go down this path is huge new spending programs, hundreds of billions in contracts to experiment with the mind-bending technology of space-based lasers and the like. The Soviets will spend billions on "countermeasures" -- more offensive warheads and decoys to beat a defensive system; advanced, perhaps supersonic cruise missiles that could scoot under a defense; elaborate new weapons to be used to attack the space-based components of the American system, and so on.

The Soviets will also build their own defense. Their national character -- plainly demonstrated again and again in the past -- will push them to copy any new strategic system that we devise. So as they begin working on defense, we'll be able to spend more billions on our own countermeasures -- new gizmos to beat the Soviet defensive system.

Amid all the intellectual dishonesty now dominating discussion of these issues, perhaps the most dishonest suggestion of all is that, somehow, creation of a Star Wars system would end the arms race. Why? Even the most idealized version of a successful defensive system will leave room for an opponent's inventiveness -- especially when you consider that a completed system can never be tested in conditions remotely resembling the ones that would prevail if it were ever actually used.

No, the very best we can expect from Star Wars is the ability to knock out most of the Soviet missiles launched against us in a war. We could never be so sure of the system as to launch an attack against the Soviets with confidence that they could not retaliate. In other words, the best we could get is a world of enormous technological uncertainty, in which both superpowers would have to calculate that a decision to launch a nuclear war was crazy.

But that is the world we have today. There is no good reason to spend hundreds or thousands of billions of dollars to recreate the status quo on a higher and riskier level of ingenuity.

And yet, the entire subculture of defense contractors and "defense intellectuals" is speedily adjusting to the idea that Star Wars is about to become the biggest game in town. The contractors are panting after the money, and a great many strategic thinkers have succumbed to the temptation to embrace the new doctrine of defense.

Why, when it offers no demonstrable improvement on the status quo, should President Reagan's Star Wars dream be so attractive to so many people? This is a baffling question. Perhaps an answer can be found in the experiments of Erich von Holst, a student of the "schooling" instinct of fish.

Von Holst removed a common minnow's forebrain, the location of that fish's instinctive shoaling or schooling reactions. (His experiment is reported in Konrad Lorenz's "On Aggression.") Without its forebrain the minnow could still see, eat and swim as before, but it had lost the reflexes that make a normal minnow reluctant to stray from its school. In Lorenz's words:

"(The altered minnow) lacks the hesitancy of the normal fish which, even when it very much wants to swim in a certain direction, turns around after its first movements to look at its shoal mates and lets itself be influenced according to whether any others follow it or not. This did not matter to the brainless fish: if it saw food, or had any other reason for doing so, it swam resolutely in a certain direction, and the whole shoal followed it. By virtue of its deficiency, the brainless animal had become the dictator!"

There is another explanation for the popularity of Star Wars: it offers a solution to the worst problem of our epoch -- not a messy, political solution, but a neat technological one. It's a very American notion: all problems are soluble, usually in mechanical ways. When Reagan speaks of Star Wars, you can hear a yearning in his voice for a fix that will make the great nuclear problem go away. Of course he's right -- it would be wonderful to find a scientific way out of the nuclear madness mankind has created. It would be wonderful to find the fountain of youth, too.

The official talk this weekend is upbeat about arms control.

But actually, Reagan administration policies, if pursued, will unravel the principal accomplishment of all previous arms contro negotiations, the 1972 ABM treaty banning most deployments and testing of anti-missile missiles.

Here again the administration's position is cynical. We are assured -- by Reagan, by Nitze and others -- that the United States will adhere to the ABM Treaty. But the Star Wars portion of the administration's 1986 defense budget now pending in Congress contains money for the development of "prototypes" of new defensive weapons that violate Article V of the treaty, which commits both countries "not to develop, test or deploy ABM systems or components which are sea-based, air- based, space-based or mobile land- based." These prototypes in the '86 budget, if approved by Congress, could be tested by 1990 -- the effective duration, apparently, of the promises to adhere to the treaty.

Our European allies recognize that there is no way to make Star Wars and the ABM Treaty compatible. That is why Margaret Thatcher has sought President Reagan's pledge that he would negotiate with the Soviets before deploying a Star Wars system. The British hope that such negotiations would somehow preserve the existing arms control regime. But can anyone imagine that the United States would spend up to $100 billion to develop a plausible Star Wars system (a conservative estimate of the development cost), and then drop the whole idea because the Soviets declined to accept its introduction after negotiations?

If the ABM treaty must go, many important officials of the Reagan administration won't mind. For despite the reassuring public rhetoric, this American government is filled with people who don't really believe in arms control, and actually prefer to live with the Russians on the basis of bad relations and vigorous competition.

Arnold Horelick, formerly the CIA's national intelligence officer for the Soviet Union and now with the Rand Corp., has described the hard-line element in the administration as convinced that the current strategic trends favor the United States. In this view, we'll be relatively better off five or 10 years from now than we are now, so why rush into new agreements with the Soviets based on today's balance of power?

There is no visible cause for optimism about the arms negotiations begining this week in Geneva. Specialists in NATO foreign ministries and many working-level officials in the United States government agree that there are no real prospects for making a deal unless the Reagan administration is willing to adhere to the ABM treaty and give up active development of the defensive weapons which it bans. But President Reagan specifically rules out using his Star Wars program as a bargaining chip.

The great irony is that the current strategic trends probably are favorable -- not if the objective is to gain a meaningful American advantage, but to get negotiated arms reductions under way. The Russians are anxious to avoid a whole new competition in space -- the threat of Star Wars has indeed gotten their attention, and it remains a potentially useful bargaining chip. Our allies are yearning for new negotiated agreements. The Reagan administration could get an effective, comprehensive treaty through the Senate, if one could be negotiated.

Negotiating a deal would not be easy. The issues are complex and growing more complex all the time, as new weapons come into both arsenals. The Soviets appear to be building an elaborate new radar installation that violates the ABM Treaty itself; U.S. planners are tantalized by the prospect that they might get a really usable defensive system to protect land-based American missile silos -- something far short of a Star Wars defense, but a neat little improvement in our arsenal that would justify deploying lots of MX missiles (because it could protect many of them in a war). Even without a full- blown Star Wars program, the fragile arms control regime now in force could easily unravel.

And yet, whatever marginal advantages the Soviets might get from their new radar or we might get from "point defense" of missile silos would not begin to provide meaningful new security to either side. Security in a world of 40,000- plus nuclear warheads can't be bought with incremental changes in your arsenal. Security can only come from confidence that the other fellow understands the balance of terror roughly the way you do, and has decided to try to live with it in an orderly way. Security is a political matter, not a technical invention.

Increased security based on political accommodation was always the promise of the arms negotiations launched by Richard Nixon and Henry Kissinger in 1969. Curiously, those two men seem assured of a relatively positive place in history because of their diplomatic accomplishments -- and despite transgressions that would sink the reputations of many other public figures.

What sort of historical reputation would a public official enjoy if he is held responsible for destroying the fruits of those earlier negotiations, and also for initiating the most expensive and dangerous round in the entire history of the arms race? Ronald Reagan, apparently surrounded by yes-men and dreamers, may not have faced that question, but perhaps he should.