If I weren't a Catholic, and if I didn't believe that the chances for nuclear war have never been greater, I would likely be saying, as are many others, that Catholic bishops are in over their heads when they introduce morality into the politics of nuclear arms.

To me, the bishops are not yet ankle-deep in these waters of controversy.

In the essentials, their proposed pastoral letter is a needed statement of defiance to temporal powers -- the Reagan administration, Congress and the Pentagon -- that they cannot expect to keep making political decisions in a moral-free context. But the letter, reasoned and cautious, lacks fire. It has none of the anger of men outraged that national security has become the new idolatry. They do not say the Golden Calf of nuclear weaponry is in need of quick smashing. It is as though, in fear of being dismissed as incendiaries, the bishops take one pace forward and then one backward.

They say, for example, that "we have judged immoral even the threat to use (nuclear) weapons. At the same time, we have held that the possession of nuclear weapons may be tolerated as deterrents while meaningful efforts are under way to achieve multilateral disarmament." This is a contradiction. To possess is to threaten. Are the bishops unaware of the history of weaponry? No crossbow, no saber, no cannon nor bomb devised by one nation has ever gone unused against another.

This contradiction arises naturally from ambivalences built into the text. One of the stated intents is "to contribute to the public policy debate about the morality of war." The bishops' call for "public scrutiny" of nuclear policies and ask for "limits" in the government's nuclear leanings.

This mildness would not stand out if, in other questions of life and death, the bishops also shied from moral firmness. To their credit, they don't. When the issue is abortion, they do not sprinkle their texts with "at the same times" nor do they modestly announce their wish to "contribute to the public policy debate." Instead, and rightly in my view, they say abortion is killing, no matter how many seemingly humane justifications an individual can make for having or performing one.

If there is no equivocation when the killing of the preborn is involved, why not when the potential killing of tens of millions of people is at stake? When the bishops opposed the Reagan administration's sending of military aid to El Salvador, where the government kills its own people, they did not call for mere "limits."

One reason the church's leaders move falteringly in its advocacy of peace is that they are uncomfortable in this new role. Until now, bishops have been builders of schools, hospitals, churches and seminaries. They have been able ministers of God's pork barrel. That work has been skilled and beneficial. But now a number of younger bishops are asking the obvious: Why put up buildings of peace in one generation, if they are to be leveled by nuclear war in the next?

American Catholicism, with a membership of 51 million citizens, is still far away from being a peace church. The tentative moves toward nuclear pacifism does little to alter the church's other massive connections to the military. ROTC flourishes on Catholic campuses, and Catholic colleges accept money for military research.

None of this is found among such peace churches as the Mennonites and Quakers. The challenge for the bishops is to accelerate, not slow, their efforts to begin a disengagement from military values. Nuclear war is only the extreme extension of those values. What risk, or sacrifice of status, is involved in saying no to a future holocaust?

But there is risk in saying no to the decisions that lead to conventional war, or no to the paying of taxes that buy weapons, or trying to educate the faithful and the whole country that Christianity in its origins was a religion of absolute pacifism.

A few bishops have been pushing hard to align the church to its original and enduring ideals. An immense educational program will be needed merely to get across the point that organized nonviolent resistence is not weakness, but a rational and effective way of settling disputes by means other than killing people. For this, the bishops should expect scorn and dismissal. They are getting a bit of this now, and it is a sure sign they are on to something prophetic.