If we are to believe Defense Secretary Caspar Weinberger, the United States has not been in such great peril since the nuclear age began. It is his apprehension verging on conviction, expressed repeatedly and at length in his latest press conference, that American nuclear forces are no longer adequate to deter a Soviet nuclear attack. An effective deterrent, he believes, must be "regained."

Hearing him say this several times indirectly, a reporter asked him directly -- four times -- whether the secretary meant "the Soviet Union could inflict such damage in a first strike that we could not retaliate?" Four times Weinberger refused to affirm that deterrence is holding. His bottom line: "I have said that I think we have to do all the things we are doing (in new arms programs) to regain an effective deterrent strength that can give us the confidence that we can maintain the peace as we have for nearly 40 years by an effective deterrent."

You could guess, of course, that Weinberger, being as smart and well-briefed as he is, is merely trying to scare Americans into voting for the next big slice of the Reagan defense budget. Certainly some of his statements were misleading enough to support that reading. He said, for instance, "we did freeze our force levels (in the 1970s) and in return the Soviet Union increased its nuclear programs dramatically," ignoring, among other items, the retrofitting of Minuteman III missiles with the Mark 12A warhead, doubling yield to 350 kilotons, and with the NS20 guidance package, improving its accuracy substantially.

But selling the budget does not seem to be the whole explanation, or the most interesting part of it.

No less likely is that Weinberger has been caught up in the crisis of deterrence that has been building among the professionals for years and is now penetrating the general public debate. To these people, what is troubling about deterrence is not that it is dangerous, unstable, costly or immoral -- all those things are in a sense manageable and forgivable -- but that it won't work: the Soviets, looking at the strategic balance, may decide they can actually get away with attacking or intimidating the United States or an ally.

The crisis of deterrence arose from the perception that Soviet power was growing to the extent that the United States could no longer count on deterring Soviet limited nuclear attack or conventional attack by threatening all- out war: it just wasn't credible. From Nixon on, as Thomas Powers has explained better than anyone, successive presidents have been working more or less explicitly toward a strategy allowing at least in theory for the use of nuclear weapons in these (hopefully) limited circumstances.

Once you do that, however, you depart the comfortable -- anyway, the familiar -- realm of successful deterrence and no war, and enter the uncertain precincts of "war-fighting," "limited war," "protracted war," efforts to "prevail," and so on. These concepts, old stuff to the specialists, have more or less guided American policy for almost a decade. Only recently, due largely to the peculiar chemistry surrounding Ronald Reagan, have they come to the attention of the general public, parts of which are stunned.

What can be said about the Weinberger approach?

First, Weinberger has a point. It is not necessarily a fantasy or a diversion to worry about the reliability of deterrence. Deterrence was invented as a theory in a climate of American strategic superiority. Long before the current wave of public protest formed, serious people of different political persuasions were wondering whether deterrence made the same sense in conditions of parity or even of some Soviet advantage.

Second, Weinberger has taken a good point too far. The results are seen in the degree of his anxiety, extreme even among the initiated, and in the particular arms and arms control policies that flow naturally from his alarm.

My feeling is that if his public statements accurately reflect his understanding of the problem, he misunderstands the problem. He has a nostalgia for a return to the super-secure days of American strategic superiority -- days that are gone forever. He sees our strategic unease now as solely the product of Soviet political decisions, when it is the product of Soviet and American political decisions and -- read Powers' piece in the November Atlantic -- of Soviet and American scientific decisions, too.

The solutions, or the ways to treat the problem in the absence of a solution, cannot be so monochromatically military as Weinberger suggests.