It has taken almost 40 years, but a lot of us have done what seemed impossible after Aug. 6, 1945. We have adjusted to the mushroom cloud over Hiroshima - at least to the extent that one hears quiet voices discussing the use of nuclear explosives, not just as a ''deterrent'' but as a reasonable weapon to be deployed by reasonable men in calm and deliberate ways.
A certain vocabulary is falling into place to support the policy of ''limited'' nuclear war. Influential strategists, civilians as well as military, talk not just of ''preemptive'' strikes and ''retaliatory'' strikes but of ''tactical'' strikes - ''surgical'' strikes. Speaking in broad terms of millions of lives, they define ''acceptable'' risks.
Politicians who have the utmost difficulty limiting inflation or unemployment or the national debt are confident they can limit nuclear warfare. Technologists who cannot always get the rocket off the pad the first time or effect a helicopter mission to Iran are ready to promise the zero-error exactitude of a ''pinpointed'' megaton hit.
At a time when we are not doing terribly well at managing the various forces in our lives, a lot of us are beginning to assume the manageability of the one force we used to assume was unmanageable.
Thirty-five years ago, during the post-Hiroshima shock, most people subscribed to the statement: ''The development of science has put war out of the question.'' Nuclear weaponry was referred to as the ''unthinkable alternative,'' ''mass suicide,'' ''insanity.'' The term ''nuclear pacificism'' won the endorsement of those who were not otherwise pacifists. This was where quarreling human beings drew the line.
It was agreed that ancient concepts like a just war and a war of self-defense had become obsolete. The nuclear bomb, indiscriminately killing everybody in its radiant path - literally scorching the earth - could not, per se, be a weapon of justice or an act of self-defense.
The philosopher Martin Buber summed up for the consensus of those days: ''How is it possible to practice restraint or selectivity with a weapon which wipes out cities with one blow?''
But that was almost 30 years ago. Now it is being suggested that one side can actually ''win'' a ''limited'' nuclear war - a hypothesis so popular that nuclear arms specialists are being driven to repeat the essential warning of former Secretary of Defense James Schlesinger: ''We can never know what degree of accuracy would be achieved in a real world.''
As if it had never been stated, Buber's argument must be restated: It is very hard to keep a nuclear war ''limited'' when a single warhead can kill tens of millions. And one can only imagine what self-discipline would be required for fingers to stay off the big buttons, once the smaller buttons had been pushed.
A couple of decades ago the novelist and essayist Arthur Koestler proposed that every year after Hiroshima be numbered to remind us that, since 1945, we have lived in a new era, possessing the power to blight the earth and the civilizations that have grown upon it. The idea seemed a little melodramatic at the time. But now it is the year 36 P.H. (post Hiroshima), and what used to be called The Bomb threatens to slip into place as part of the norm, like the cannon after the crossbow.
With reason, we are alarmed that we are not more alarmed. As conservative, as apolitical a group as the American Medical Association has voted to inform the President and Congress about the ''medical consequences of nuclear war.''
As if Hiroshima were not evidence enough! How could we forget? But we do forget, just enough so that we think we can manage a quarter-nuclear war, or maybe a half-nuclear war - we'll know when to stop.
Three decades ago Buber understood the temptation. His words may sound simplistic, like a lot of the words written then. But when we hear the sophistication of the ''limited'' nuclear war scenarists, we must ask: Is this not one subject to be simplistic about?
''If you will not stop now,'' Buber wrote, ''a moment must come - and perhaps very soon - when it will no longer be possible to stop.
''The game plays with you.''