In the best tradition of making a long story longer, the third draft of the Catholic bishops' pastoral letter on war and peace is more than twice as long as the first draft and 50 percent wordier than the second. At 34,200 words, it is about 17 times longer than the Sermon on the Mount, Christianity's first pastoral statement on peace.

Times change, it is said. They do, but the passage of time between the second draft last November and the third draft to be debated today and tomorrow in Chicago is small justification for the weaknesses that have turned the statement into what one dismayed bishop has called "just another discussion piece." He will offer 40 strengthening amendments.

The second draft criticized the MX missile program. The third draft does not. The second draft quotes Cardinal John Krol's 1979 statement before Congress: "Not only the use of strategic nuclear weapons, but also the declared intent to use them involved in our deterrence policy, are wrong." Krol's thought is referred to but not quoted.

Mutings of tone occur. In draft two: "We believe religious leaders have a task . . . to set the limits beyond which our military policy should not move. . . ." In draft three: "We believe religious leaders have a task . . . to suggest the limits beyond which. . . ."

Although much of the letter is valuable and strong, the pullbacks diminish its overall impact. If, as the draft states, we are facing "a moment of supreme crisis," why back away from morally confronting in unequivocal language the mentality and the leaders who prolong the crisis? If "the arms race is one of the greatest curses on the human race," why not a statement that echoes the anger of the prophets rather than the analytical nuances of a seminar?

Like a father welcoming back a prodigal son, the Reagan administration, which was publicly piqued at the second draft, said the third attempt was "substantially improved." The administration, which views the Soviet Union as an "evil empire," was pleased that the third draft heats up the rhetoric about the enemy: the "Soviet imperial drive," the "Soviet military expansionism."

As disappointing as the third draft is, it needs to be remembered that it is not yet final. The five bishops who signed the current draft are merely offering it to the full body of nearly 300 bishops. There will be votes on amendments.

It appears that in one instance, protests from other bishops have already caused the five to return to the stronger language of the second draft. The second draft had called for a "halt" to the testing, production and deployment of new nukes, while the third proposed to change "halt" to "curb." Now, thanks to the protests, it's back to "halt."

One unresolved question is how the full body feels about the new warmth from the Reagan administration. Does it also feel comfortable that National Review, which has consistently and often snidely ridiculed the hierarchy for butting into politics, now finds the third draft "a substantial improvement over its predecessor"?

One bishop, in an interview, laughed at these embraces. "They haven't read what we wrote," said Bishop Thomas Gumbleton, one of the five on the drafting committee. "We are still saying no to first use, still saying no to a counter (deterrence) policy and still saying no to a limited nuclear war." This is "opposite Reagan's policy."

Regardless of how the final votes go, i.e., whether the bishops see the changes as substantive or merely clarifying, the pastoral remains a whisper where a shout is needed. It quotes Caspar Weinberger but not Dan Berrigan. It concentrates on East-West conflicts. Why not North-South as well? In 1978, U.S. military sales to Third World countries totaled $11 billion.

It avoids addressing the question of how Catholicism can seek to become a peace church without using occasions like this to announce a return to the principles of pacifism as taught with unmistakable clarity by Christ.

To be a partial peace church isn't enough. An adaptation to the times isn't needed. Nowhere in the Sermon on the Mount does it say "Blessed are the adapters. . . ."