By this time we (meaning the vast majority of the human race) know that a nuclear war would do enormous damage. There is disagreement among the technicians and scientists over whether a general exchange of nuclear weapons would merely cripple Western civilization, or wipe out the entire human race. That it would, at the very least, set us back to the Stone Age is not in serious question.
What is in question is whether anything, and if so, what, can be done to reduce the danger.
The plausible and reasonable answer begins with the location of most of the weapons. There is no doubt about where they are. The United States at present has in its military arsenal 8,297 nuclear warheads mounted on long-range strategic delivery vehicles. The Soviet Union has a similar number. (The precise number is in dispute in the West.) If the total of some 16,000 warheads were fired by the two superpowers at each other, there would be not only a holocaust in those two countries but possibly an end to all human life on the earth.
No one else has anything comparable in numbers of nuclear weapons.
The British have 192 warheads at sea on their Polaris submarines. The French have 80 at sea, 18 on land. The Chinese have 14 on land. (The US, USSR, British, French, and Chinese also have numbers of shorter-range warheads, but I am arbitrarily limiting myself here to the long-range variety.)
Other countries are presumed to have nuclear weapons, although denying it. It is generally taken for granted that Israel and South Africa have jointly produced such weapons. India probably and Pakistan possibly have also obtained them. Many others have the technical ability to build them if and when they choose.
But only the US and the USSR have such weapons in the thousands, and only those two think and act in terms of the possibility of a mutual exchange of such weapons in such quantity.
In other words, the kind of nuclear exchange we have recently seen dramatized in ''The Day After'' is something that is peculiar to the US-Soviet relationship.
Other countries have the ability to do grave damage to each other. The British and French together have enough nuclear power to do vast damage, but against whom would they use it? Certainly not against each other, or against the Soviets or the US. They could be overwhelmed by some 30 times.
Other countries have deterrent capability. But no reasonable scenario leading to a general holocaust can be written around anything but the US vs. USSR rivalry.
The real danger, therefore, lies not only in the weapons themselves, but in the hostility between the US and the Soviet Union which first caused the accumulation of the weapons and then makes the massive use of them conceivable. If the hostility could be removed, or reduced, the problem of controlling and reducing the number of weapons would be relatively easy, and manageable.
The present number of weapons in both the American and Soviet arsenals is appalling. Without new agreements on limiting the numbers, then those numbers will continue to go up, not down. The Soviets have walked away from both the strategic and the European theater weapons' talks. No date for a resumption of talks has been set.
So, the danger of a massive nuclear exchange exists. It arises out of a mutual sense of hostility between the US and the Soviet Union. The serious question, therefore, is whether anyone can do anything useful to attack and perhaps begin to wear down that mutual sense of hostility.
Efforts are being made. The prime laborers in this vineyard are the West European allies of the US. They have kept open their connections with the Soviets and have repeatedly restrained some of the inclinations of the Reagan administration in Washington.
But President Reagan continues to operate on the assumption that the Soviet Union is ''evil'' in nature and the cause of the world's major problems. The latest example is his assumption that Moscow is the cause of Syria's refusal to withdraw its troops from Lebanon to accommodate Mr. Reagan.
And the Soviets, of course, operate on the assumption that most of their difficulties are caused by the US. Need this condition of mutual distrust continue, and, if so, for how long?
To be continued on Thursday