With De'tente II dawning, they say that this time we will not be as euphoric and foolish as the last disastrous time around. Judging from the self-congratulatory hyperbole accompanying the U.S.-Soviet agreement on INF that has opened the way to a fall Reagan-Gorbachev summit, don't bet on it.

President Reagan has called the INF agreement historic. True. Previous arms control agreements merely capped the growth of nuclear weapons. This one reduces them. Warheads will ostentatiously be destroyed. An entire class of weapons, those with a range between 500 and 5,000 kilometers, is to be abolished. Better still, these reductions are not just radical, but asymmetric: the U.S.S.R. will remove 1,565 warheads; the United States 436.

And yet such eminently sensible moderates as Les Aspin and Henry Kissinger argue that this INF agreement will actually injure Western security. They are not just being perverse. The harm of an INF treaty is real.

The claim of treaty supporters that American INF weapons (Pershing 2s and ground-launched cruise missiles) were deployed in Europe solely to offset Soviet SS-20s aggressively deployed in the late 1970s -- and therefore that removing both sides' weapons is all we ought to want -- is false. The Pershings and cruises were deployed for an additional reason: to offset the real military imbalance in Europe, which is conventional. Take away nuclear weapons and the Soviets have an overwhelming military advantage that they can use to blackmail and dominate Europe. That is why NATO's defense has always rested on the threat of nuclear retaliation to any Soviet attack, conventional or nuclear, on Europe.

The question has always been: what kind of nuclear retaliation? The threat of a nuclear counterattack that comes from a missile field in Montana is not credible. The threat of a nuclear counterattack that comes from American missiles in, say, Germany, is not altogether credible, but the resort to nuclear weapons by local American forces about to be overrun is still far more credible than the resort to nuclear weapons by remote and secure transoceanic American forces. What Atlanticists like Aspin and Kissinger fear is that, with the removal of American INF forces, the defense of Europe becomes decoupled from the defense of the United States, and Europe, now more vulnerable to Soviet conventional superiority, detaches itself over time from an unreliable American ally and seeks accommodation with the Soviets.

These arguments are sound. They are, however, not enough to force rejection of the INF deal, because they ignore several mitigating circumstances and they ignore the greater harm that rejecting the INF treaty at this point would do to Western security. First, the United States still has other nuclear weapons in the European theater that can be used to deter Soviet aggression. These include nuclear-armed bombers and submarine-launched ballistic missiles. And there are hundreds of battlefield nuclear weapons in Germany, enough to give any Soviet military planner pause before daring to exploit his conventional advantage.

More important: if the real danger of an INF treaty is political and psychological (the perceived decoupling of America's defense from Europe's), then one must consider the political and psychological consequences of the United States' now reneging on an INF deal that the United States itself proposed in 1981. At that time the "zero option" was more attractive for the West than it is now: the Soviets were sprouting triple-warheaded SS-20s weekly and the West had deployed nothing. The offer of zero for both sides helped European governments overcome a very powerful pacifist opposition and thus allowed American INF deployment in the first place. For the United States now to reject its own offer -- as Gennadi Gerasimov cleverly put it, to refuse to take yes for an answer -- will do more damage to U.S.-European relations than the limited decoupling that the INF deal entails.

On balance, then, the INF treaty is tolerable. But just so. And all the ballyhoo you will soon hear about its historic import, its ushering in a new age, its turning a whole class of nukes into ploughshares, is rubbish.

But instructive rubbish. The discrepancy between the euphoria engendered by this upcoming treaty and its real effect on our security highlights perfectly Western illusions about arms control. If the most historic, radical, numerically asymmetric arms cuts ever have a minimal (negative, in fact) effect on Western security, what does that tell us about arms control?

That arms control agreements are mostly symbolism. They are meant principally to demonstrate to Western publics that the arms race is under control. They have little to do with security and less to do with peace.

Real de'tente will issue not from nuclear treaties but from entirely different kinds of agreements. Hostility between East and West will be reduced, and with it the chance of war, when the Soviets demonstrate two historic turns: that they are not bent on extending their rule (to such outposts as Afghanistan, Nicaragua and Angola) and that they are not bent on destroying the human spirit where they do rule, i.e., when they convincingly begin dismantling the apparatus of totalitarianism. Progress in these areas, what the diplomats call "regional conflicts" and "human rights," is real progress toward peace. Everything else is atmospherics. A less polite word for that is illusion.