The most significant achievement of the nuclear freeze movement thus far is its challenge to the administration's lopsided assessment of the Soviet threat. The threat assessment is central to the nuclear debate. The freeze idea is simplified code, symbolizing a rising public fear and frustration at what is perceived as a growing danger of nuclear war, but its advocates are not unilateral disarmers, and they seek more than a literal freeze. They represent a grass-roots demand for the prompt resumption of serious, comprehensive nuclear arms talks without preconditions.

The movement reflects a potentially momentous public understanding that massive nuclear overkill and unstoppable delivery systems on both sides make nuclear war between the superpowers not only unwinnable but also mutually catastrophic; that the enduring reality in U.S.-Soviet nuclear relations is parity and stalemate; that the Reagan decision to build more numerous, more powerful, more accurate weapons is unnecessary and dangerous; that the Soviet leaders, while they will not stand still for a new U.S. effort to effect a favorable shift in the strategic balance, clearly prefer a stabilizing agreement to a new arms race.

The administration argues that the Soviet Union has achieved, or may soon achieve, a clear "nuclear superiority" and that this poses a dire threat because the Soviets are prepared to use it as an instrument of diplomatic coercion against the West. The administration's policy has been to launch a massive arms buildup, including significant new nuclear weapons. For the far-out anti- Soviet Reaganites, the goal seems nothing less than restoration of U.S. military superiority, which most clear-headed observers regard as illusion. But even for administration moderates, the effort to play "catch-up" is a prerequisite to arms control negotiations. In its own view, the administration was forced prematurely into theater nuclear force talks by the outbreak of anti-nuclear feeling in Western Europe, and it seems quietly determined to make sure these talks do not produce an agreement that would forestall deployment of 572 new U.S. missiles in Europe. So far its stonewalling has been quite effective. The U.S. "zero-option" proposal is a sure non-starter; more broadly, the attempt to isolate the control of "tactical" nuclear weapons is artificial and futile. A purely European nuclear agreement is beyond reach for the reason that many of the weapons systems targeted on that area (from both sides) are based outside the region. To be meaningful, a European nuclear arms agreement must be part of a wider agreement covering intercontinental systems, but this requires a return to SALT (or START).

The administration has strongly opposed the early resumption of comprehensive talks on the grounds that this would inhibit the U.S. military buildup. The contrary argument of the freeze movement is that the nuclear balance is not unfavorable to the United States and that the resumption of comprehensive nuclear talks should be treated as a matter of utmost urgency. The groundswell of public support for the latter view has pushed the president to speak publicly of possible comprehensive arms talks as early as June.

In defending its massive arms buildup and negative negotiating stance, the administration has relied on the same abstract, narrowly mathematical arguments that were used by Paul Nitze and his band of nuclear theologians to frustrate Senate ratification of SALT II. The central assertion is that the Soviets will soon have a theoretical ability to knock out 80 to 90 percent of our ICBMs and that they might indeed try such a "limited" attack with the aim of cowing the U.S. president into forgoing any retaliation at all for fear of bringing down the total holocaust. It seemed astonishing at the time, and seems equally so in retrospect, that Nitze's senatorial and journalistic auditors allowed him to slide over the extremely awkward fact that such a Soviet first strike would leave untouched at least the entire U.S. submarine- launched missile force and probably most of the U.S. bomber force--meaning that the Soviets would be vulnerable to retaliation by at least 50 percent of our nuclear hitting power, somewhere between 4,000 and 6,000 warheads. Even more surprising is the fact that two years ago public opinion accepted the Nitze argument that SALT II would lock us into a permanent inferiority--an assertion without any factual basis, as the treaty imposes no prohitions on the deployment of the B1, the MX, the Trident submarine or the Trident missiles I and II.

The climate of opinion is palpably changing. What is new is the assertiveness of senatorial and public reaction to the administration's flawed reasoning. Fortified by spreading evidence of common sense at the grassroots, Sens. Kennedy, Hatfield, Cranston, Hart and Levin--to name only a few of the leaders--are beginning to puncture the hermetically sealed thought chambers in which the nuclear theologians live, and to expose their esoteric calculations to public scrutiny. The introduction of political fresh air into these arid domains is healthy. It shows up the thinness of much of the data, the highly subjective assessments of Soviet policies and intentions--and, perhaps most important, the divorcement of fine-spun scenarios from the governing political realities in both Soviet and American societies.

The immediate goal should be ratification of SALT II as the basis for prompt resumption of comprehensive arms control talks.