We print on T the opposite page today an article by deputy Secretary of Defense William H. Taft IV, complaining about a recent editorial on DIVAD, the Army's new divisional air defense gun. Mr. Taft takes us to task on two counts. The first is for having argued, as he reconstructs it, that DIVAD ought to be killed not on the merits but as a symbol and example, proof that the higher-ups in the Pentagon have the strength to say no.

That of course is not what we said. We told a little of the weapon's history -- how it has never been too good at taking tests; how its test results had caused Defense Secretary Caspar Weinberger himself to hold up further procurement last year; how its manufacturer, Ford Aerospace, had then misrepresented its most recent test results. We concluded that DIVAD is "a costly weapon, the need for which is not completely clear and in whose performance no one can have great confidence on the record so far." That is why we said it should be killed, which we would have thought was plain enough in English, even if not in French. We then went on to observe that the DIVAD decision would also have a bearing on the credibility of the procurement process, that "if it can pass muster in its present state, the message is that any weapon can." We still think that.

Mr. Taft's second point, as he himself observes, "involves a more serious issue," which is just as well. We said in the editorial that there is growing pressure on the weaker weapons the services want because the defense buildup was underpriced and "the defense budgets now projected, large as they are, will not buy all the weapons the planners earlier said they would." Mr. Taft says this is an issue long since disposed of, that survives only in our word processor. He wishes it were so.

1.In the high-inflation 1970s, weapons costs greatly outran estimates. Some people argue they always will, that a bias in this direction is built into the procurement system. On that basis the General Accounting Office has suggested the Army may not have enough funds in sight to cover its modernization program and that the present five-year defense program "could absorb $173 billion to $324 billion more than planned." The Air Force itself said in 1983 that if past cost growth rates persisted, "only 77 percent of the planned acquisitions could be carried out within programmed budget levels." But administration officials say they have largely cured the cost growth problem. Thus Mr. Weinberger, in a covering letter to Congress on this same Air Force study, warned against taking it to mean that "historical program cost problems would continue in the future." Mr. Taft might prefer it not to, but this debate goes on.

2.There continues to be a question whether enough money has been allowed in future budgets to man and maintain all the weapons now being bought. That is particularly a question with regard to the 600-ship Navy. There are senior people in the Pentagon itself who have serious doubts about the Navy program on this score. There are also doubts among members of Congress. The Congressional Budget Office, hardly an alarmist organization, said in a study earlier this year, "Concerns have been raised about the costs of attaining and maintaining this 600-ship Navy. Such concerns could be well founded." Former CBO director Alice Rivlin suggested in testimony in 1983 that the Army, which is at work on 14 major new weapons systems, might have a similar problem.

3.There is also concern about the likely cost of future weapons now just entering the budget as research and development items. On these the alarm has been sounded by, among others, Sen. Sam Nunn, ranking minority member on the Senate Armed Services Committee. The weapons include a new destroyer, new tactical fighter, new transport plane, new vertical takeoff plane. Mr. Nunn says the Pentagon cannot afford them; he has urged that the list be pruned. The senator is not one of those people who "have worked too hard for too long to cut the defense budget in recent years."

Mr. Taft of course is right that Congress has cut the defense budget, this year in particular. There are differences over how much to make of these cuts. Some, like Mr. Taft, say Congress cut muscle and bone. Others say it cut mostly fat and air. As the deputy secretary's letter makes clear, what is mostly at issue in this dispute is future blame. There are bound to be problems with the defense buildup in later years. Some costs will exceed predictions; some weapons will not work; some threats that are now foreseen will not materialize (and other threats that are not foreseen will). The question will then be whose fault this is. Critics will blame the administration for not having had a good plan. The administration will blame Congress for having cut the budget. It is a silly game, and Mr. Taft is already playing it.