IN THESE VOLUMES, which read as if they were a series of position papers written for Ronald Reagan and Edward Kennedy, two think-tanks ask Americans to think seriously about the future. They start from the same place, but unsurprisingly they tend to reach different conclusions.

The 30 Hoover Institution essays, many by well-known economists and social scientists (Friedman, Greenspan, Weidenbaum, Teller, Lipset -- to name a few), would, in common parlance, be considered "conservative." But as with the term "liberal," which many would label the Brookings Institution, the term has lost all meaning.

Both books begin with a sober, even somber, view of the 1980s. Agreeing that the next decade will be, as the Hoover volume puts it, "a harsher, more exacting, and more perilous age," Brookings diverges on the remedy. In an age of "limits," the Hoover authors plump for "limited government," while those from Brookings would tinker with the governmental apparatus and try to reform it.

They differ also in general attitude. Hoover's 32 experts believe that Adam Smith economics will help us "save more than we spend, work more than we play, and spend more on defense and less on welfare." While denying that they want a "garrison state," their recommendations constitute precisely that.

To the Brookings' experts, "the prospects for achieving a healthy economy and maintaining peace are not good." To them, the system itself is in crisis, which means, as Jsoeph Pechman puts it, Americans should "stop blaming the particular leaders who happen to be in office for what is wrong and [begin] to look hard at the system in which they work." That is age counsel; and it is a pity that Pechman's colleagues did not follow through on it. In the main, they want to tinker rather than address what Brookings' James Sundquist (in the best essay of all, "The Crisis of Competence in Government") calls "severe institutional and structural problems."

Among the essays, which address the entire range of public-policy questions, a few may be singled out for particular attention. All, however, deserve careful reading.

Take economic policy. Hoover's Milton and Rose Friedman plump for an "economic Bill of Rights" to set limits on government intervention in the economy. They would establish a full-fledged laissez-faire economy by constitutional amendment. Alan Greenspan and Murray Weidenbaum strike similar notes.

But Barry Bosworth, a former Carter administration official, believes in continued governmental action to control the economy. He does concede, however, that a "program of general wage and price controls, restrictions on housing and energy demand, and a continuation of slow economic growth are not easy measures to sell even on a temporary basis."

Or consider energy problems. Brookings' Hans Landsberg assumes that continuing action by the federal government is necessary. Hoover's Thomas Moore, however, takes the opposite tack: "Private sector incentives, following the dictates of Adam Smith's invisible hand, will provide energy at the cost of finding and developing it." Moore would even turn nuclear power, including disposal of nuclear wastes, over entirely to private companies.

Both camps attempts to resurrect the past (rather, an idealized version of the past) merely flounder. Neither recognizes that Americans, and others, face not a crisis but a coalescence of crises -- "a climacteric," as Willis Harman (not one of the authors) asserts, that "may well be one of the most fateful in the history of civilization."

Defense policy points up differences between the two groups even more clearly. William Kaufman of Brookings maintains that "Americans [should] avoid panic, stop exaggerating Soviet capabilities, and call a halt to the unnecessary denigration of their own. The Soviet Union in 1980 is not a military giant and the United States is not a military pygmy." Detent is not a dirty word for Brookings -- exactly the opposite of Hoover's authors. Fred Ikle trumpets a warning about what he says is America's declining armed strength; Amoretta Hoeber and Joseph Douglass assert that the Soviets believe they can fight, survive, and win a nuclear war.

What is one to make of such divergent views from some of America's best-known deep-thinkers? Several lessons may be drawn.

Expertise depends on ideology. None of the authors exposes his value preferences, save in Adam Smithian or post-Keynesian platitudes. That means that whether one accepts one analysis or its counterpart depends in turn on the reader's predilections.

The 1980 prsidential campaign is being conducted in almost a total vacuum insofar as discussion of the important issues is concerned.

There are specialists panting in the wings should Reagan or Kennedy replace Jimmy Carter. Many of them wrote the papers in these books.

The issues are too complex for Mr. T. C. Mits (The Celebrated Man in the Street) to comprehend. He can understand inflation and unemployment, for they hit home, but almost everything else in these books is beyond his ken -- or even his interest. These are essays for others experts.

Neither group presents adequate ways to resolve the many problems of the harsher and more exacting age into which Americans are entering. Both laissez-faire and post-Keynesiansim are intellectiualy bankrupt.

In implicitly asking Americans to think seriously about the 1980s (and beyond), the several authors have rendered a singular service. Not that such thought will come easily -- or even at all. A nation of avowed pregmatists, we have a history of not recognizing problems until they become crises -- until, that is, it is usually too late to mount a rational reponse. Charles Lindblom of Yale calls this "the science of 'muddling through'," -- but policy-making is less a science than a series of cobbled-up compromises that reflect the short-comings of pluralism as a political order.

Pluralism has broken down, as Prof. Theodore Lowi has shown in his brilliant The end of liberalism: The Second Republic of the United States. One reason is that pragmatism no longer is adequate. It was all right in the past when the United States enjoyed living in a set of accidental, nonrepeatable, and nonsustainable environmental factors unique in human history -- factors that allowed it to wax large and strong and affluent.

That time has ended, as these essays show. The further message is that no one quite knows what to do. As never before, save perhaps in the Civil War, American institutions are being challenged. Whether they are up to the need is a question, as lawyers say, upon which the jury is still out. The problem is really far deeper than any of the authors of these two books cares to admit. The system itself is indeed in crisis, but for the most part systemic problems are not addressed, and the remedies proffered are mere Band-aids to be plastered on the outside of an unwieldly constitutional structure.