For decades, men have sought wistfully for one simple answer that would give them final dominion over the nuclear arms race. In the view of some experts, the answer is to be found in a treaty that would stop the race. In the view of others, it could be a superweapon that would provide the ultimate defense. Almost like a holy grail, the answer has lain out there somewhere, just beyond the grasp.
Even some of its defenders admit that President Reagan's vision for the 21st century - an antiballistic-missile defense - may prove to be as unattainable as the grail.
And even should vision become reality, the past pattern of the arms race suggests that the Soviets might find a way around, or through, the defense system. They might also find a way of blinding it. Then the Reagan vision would become a space-age Maginot Line, much like France's World War II barrier that proved too static to stop the German Reich. This is only one of many concerns that critics have as debate opens on President Reagan's call for intensified study of possible antimissile defense systems.
According to presidential advisers, one of Mr. Reagan's aims was to stimulate debate on the subject. But the debate that he has set off so far may include a bit more criticism from American scientific experts than he had reckoned on. These scientists are the very people who are supposed to rally to the President's call and take a new look at research being done in the field of antimissile defenses.
Not surprisingly, the Reagan idea has also been attacked by Democrats in the Congress. In a formal response to the President at the end of last week, they accused Reagan of seeking to distract the public from economic problems with talk of space-age weapons and allegations of American nuclear inferiority.
Equally unsurprising, perhaps, was the Soviet response to President Reagan's proposed new look at ways of defending against nuclear missiles. On March 26, Soviet leader Yuri Andropov declared that Reagan's new proposal was aimed at ''disarming the Soviet Union'' and would lead to a runaway nuclear weapons race. In some of the strongest language ever used by a Soviet leader about an American leader, Mr. Andropov accused the President of lying about Soviet military strength.
The White House will no doubt dismiss both the Democrats and the Soviets as engaging in partisan attacks on the President's idea. Indeed, Secretary of Defense Caspar W. Weinberger has characterized Andropov's comments as ''the simple, standard Soviet disinformation.''
What may be more difficult to dismiss is the criticism from US scientists who over the past two decades have engaged in research on antiballistic missile (ABM) defenses and futuristic weapons. Aside from a general consensus that Reagan's idea did not appear to have been carefully thought through, the scientists' criticism breaks down into two basic contentions:
* That the President's idea offers a simple and most likely unrealistic hope for the future, which might divert the American government and people from efforts to negotiate arms control agreements with the Soviets.
* That the Soviets will almost certainly be able to respond to any major ABM development with new weapons of their own (space mines, for example) which the Kremlin could produce at a fraction of the cost of a complicated American defense system. The result, the scientists say, would be an intensified arms race.
What most seemed to intrigue a dozen odd scientists and arms control specialists interviewed by this reporter was the possibility that Edward Teller, the father of the hydrogen bomb, was behind much of the President's thinking on ABM systems. But Teller, now with the Hoover Institution, is one of the President's scientific advisers. His work is admired by George Keyworth, science adviser to the president and director of the Office of Science and Technology Policy. According to the weekly financial publication Barron's, which interviewed Keyworth at the end of last year, the science adviser calls Teller ''my second father.''
Teller has been working on ABM problems, and according to some scientists with access to classified information, the veteran atomic scientist thinks that he has got some of the answers which the White House is seeking. (Teller, who could not immediately be reached for comment, has been trying to get some of his ideas declassified so that they can be brought into public discussion.)
''Teller's ideas are much wilder than those which the President came out with ,'' said Herbert York, a former undersecretary of defense for research and engineering and member of a negotiating team for the Carter administration that met with the Soviets for talks on banning antisatellite weapons.
Mr. York, who is currently director of the Program in Science, Technology, and Public Affairs at the University of California in San Diego, said that, speaking at a very abstract level, he agreed with the President that the nation's main emphasis should be on its defenses rather than on offensive weapons.
''On the other hand, there's absolutely nothing in sight that can provide a defense against missiles,'' said York. ''I think I know what most of the possibilities are.''
''When it comes to rallying to the President's call, there are almost certain to be a lot of people out there with ideas to sell,'' said York. ''But in what you might call the top levels of the scientific community I don't really expect to see much enthusiasm.''
More harsh in his criticism was Richard Garwin, a physicist with the International Business Machines Corporation who has done extensive research on nuclear weapons and possible ABM systems.
''I think the President is a novice in the field,'' said Mr. Garwin. ''The Soviets will evade or destroy any system we can devise. . . .The problem is to defend the ABM system itself.''
Garwin has joined with 16 other scientists and arms experts in calling on President Reagan to ban all weapons from outer space. A 1974 treaty between the US and the USSR pledged both sides not to deploy an ABM system except to protect certain limited areas, such as the region surrounding either country's capital or its primary missile sites.