In the midst of the debate about nuclear weapons there is a simple moral issue that puzzles me. This is the morality that underlies the concept of ''deterrence.'' In itself deterrence seems a very sound and good approach to any future war. Both sides will put themselves in positions where the outbreak of hostilities is to their disadvantage. It may be hoped, therefore, that hostilities will never occur.
The way in which deterrence works is very simple in theory. The power of nuclear arms will be kept in a prodigious balance, establishing an umbrella of fearfulness that will impede either side from giving vent to aggressive tendencies. ''If you shoot at me,'' it says in effect, ''I'll shoot back at you.'' Since shooting in an era of nuclear arms means destruction of millions of people and untold damage to the earth itself, the obvious conclusion is that it is better not to begin. In practice, of course, nuclear deterrence gets to be very complex, as means are devised amid a constantly changing technology to keep each side capable of a retaliatory stroke. Such matters are beyond the scope of this essay.
The underlying concept that so many good men and women seem to be accepting uncritically is, basically, the concept of revenge. Let us consider how the doctrine of deterrence might actually work. Through unfathomable maliciousness, or perhaps through accident of misinformation, a nuclear stroke is launched against the United States. Cities are laid waste; as many as 50 million of our citizens are killed or maimed. According to plans long ago agreed to, we must now loose our missiles, destroying an equal number of the enemy and laying waste as many of his cities. In doing so, we may very well upset fatally the ecological systems by which our planet lives.
In pre-nuclear conditions the doctrine of retaliation was acceptable and rational. It went against the Christian injunction to transcend the old standard of ''an eye for an eye and a tooth for a tooth''; but in the rough world of reality it did well enough. Individuals might turn the other cheek and survive, but nations had to rely on hitting back at the enemy. Indeed if war is justifiable at all, the doctrine of retaliation is inescapable. Under today's conditions, however, serious questions arise.
To retaliate after a first nuclear strike is to engage in such acts of indiscriminate destruction and such portentous danger to all life as to imitate the actions of a madman. It is to lift one's behavior into a different realm and dimension from that of delivering a mere counterstroke. It is to move from striking back at an enemy to wreaking a wild and utterly barbarous revenge upon him. One may wonder, indeed, whether in the instants following a first nuclear strike, amid the inconceivable wreckage and scenes of death, any human being would actually bring himself to effect such a retaliatory stroke as would reduce an opposing nation to the same state.
The doctrine of revenge has always been conceived of by moralists and philosophers as self-defeating. In the great dramas dealing with this theme the character seeking revenge has brought about his own downfall more surely than the downfall of his enemy. Often the ruin is portrayed in psychological forms, as hatred and unrestrained violence devour the core of a man's being. More elementally, it is portrayed as a futile course leading to mutual destruction and to havoc throughout a wide and illimitable expanse of life.
The question about the seemingly plausible doctrine of nuclear deterrence is whether it can be made the basis of policy without leading to ultimate psychological and physical ruin. Can any policy ever work that is based upon a morality held by wise men of all generations to be abhorrent? Some may say that morality is a luxury not to be indulged in where the life of a nation is at stake. But without morality, and without a profound concern for moral issues, a nation is doomed in spite of itself.