FAMILY AND NATION. By Daniel Patrick Moynihan. Harcourt Brace Jovanovich. 207 pp. $12.95.

IN THE THREE chapters of this book, originally given as the Godkin Lectures at Harvard University, Daniel Patrick Moynihan considers the state of the American family, finds it in jeopardy, and proposes that a concerted national effort be made to preserve and strengthen it. His argument is not that we should enact legislation specifically aimed at problems of the family, but that we should make family- preservation a stated policy of the national government in the same way that the Employment Act of 1946 stated "the federal government's policy and responsibility 'to use all practicable means' to promote 'useful employment opportunities' for all those able, willing and seeking to work." As Moynihan puts it:

"In the nature of modern industrial society, no government, however firm might be its wish otherwise, can avoid having policies that profoundly influence family relationships. This is not to be avoided. The only option is whether these will be purposeful, intended policies or whether they will be residual, derivative, in a sense concealed ones."

There are two basic assumptions at work here: the first being that the preservation of the family is desirable, the second that the government can and should take positive action to assure it. There might seem, at first glance, to be no clear national consensus on the first question, since divorce rates are high and, according to one study cited by Moynihan, "sixty percent of children born in 1984 can expect to live in a one-parent family before reaching age eighteen." Moynihan himself concedes that "by the mid-1980s, it was clear that family disorganization had become a general feature of the American population and not just an aspect of a frequently stigmatized and appropriately sensitive minority community."

But by no means does it necessarily follow that because the family is in a state of disintegration, there is no consensus in favor of protecting it. Though such matters can only be sensed rather than proved, there now appears to be a clear national mood -- a mood cutting across all racial and ethnic lines -- in favor of traditional American values and institutions. There seems little reason to doubt that the overwhelming majority of Americans agree with Martin Luther King Jr., who said in 1965: "Family love not only educates in general but its quality ultimately determines the individual's capacity to love. The institution of the family is decisive in determining not only if a person has the capacity to love another individual but in the larger social sense whether he is capable of loving his fellow men collectively. The whole of society rests on this foundation for stability, understanding and social peace."

Only the irresponsible would dispute that this is one of the essential givens upon which our society rests, or that the widespread and various threats to family stability are matters of deep national dismay. In particular, it is cause for the most intense concern -- concern that has yet to be reflected in public policy -- that a direct result of family breakdown has been the creation of a new subclass composed of poor women and children. "The term feminization of poverty is useful," Moynihan writes. "It gets halfway to the point, but only halfway. It is not females who suddenly succumbed to poverty during (the 1980s) but children, of whom slightly more than half are male." While poverty among the old has been drastically reduced by Social Security, Medicare and other programs, poverty among the young is rising at almost epidemic proportions. "It is fair to assume," Moynihan writes, "that the United States has become the first society in history in which a person is more likely to be poor if young rather than old."

That our society regards this as desirable is inconceivable, yet it is taking place and its connection to family disorganization is unquestionable. So what do we do? Moynihan argues, and he makes a very strong case for it, that government at all levels must take into account the actual or potential effects upon families of other programs seemingly unconnected to family welfare. None of these is more pervasive than tax policy, and Moynihan properly turns to it first. The exemption for dependents, "a children's allowance built into the tax code," has been increased from $600 in 1948 to $1,040 in 1985, yet "to maintain the value of the personal exemption of a generation past, by one measure, would call for approximately a $5,600 exemption at present." In other words, without even being aware of it we have allowed "a powerful national family policy" that exempted most of the cost of child-rearing from taxatio to become an equally powerful policy that is, to all intents and purposes, anti-family. The correction of this is a matter on which liberals and conservatives should be able to agree:

"To be sure, we do not know the processes of social change well enough to be able to confidently to predict them, far less to affect them. What we do know is what we generally value as a society and what generally we think is conducive to the things we value. We value self-sufficiency. We are offended by poverty. It follows that we should not tax individuals, much less families, to the point where they are officially poor and potentially dependent. We now do that. Would recent trends in family structure change if we stopped doing it or did it to a lesser degree? We do not know. But it is not necessary to know (and probably not possible). What is necessary is the willingness and ability to act in some coherent manner in accordance with some coherent objective. We can act if we can agree, and this is matter on which we can agree. Do not tax people into poverty. Do not tax them below their family's needs. We can further agree that in this matter we are not so much changing things as restoring what was once in place, remembering answers we once thought obvious. Is this not a common ground? A possible common ground? What else?"

So the proposed increase in the exemption to $2,000, as contained in the House tax-reform bill, is a step in the right direction. Another that Moynihan strongly endorses is "a uniform, national benefit level" in the Aid for Families With Dependent Children program, which he believes would "declare a genuine national concern for children"; he acknowledges the dependency problems this program has raised, but correctly gives first priority to the needy children. He believes that the Child Support Enforcement program, already demonstrably effective, should be pressed as vigorously as possible: "If the informal sanctions of society will not enforce the principle of legitimacy, let the state do so. Hunt, hound, harass: the absent father is rarely really absent, especially the teenage father, but merely unwilling or not required to acknowledge his children's presence." And he insists that the government must fight drug abuse far more effectively than it now does, one good reason being that its effects on family stability are deleterious indeed.

MOYNIHAN says all of this in a book that, though brief, contains a sweeping view of the American family and a no less sweeping indictment of the American body politic for permitting it to fall into such disrepair. We have always prided ourselves on being a nation of families, and familial images are central to our national mythology, yet we are pursuing courses that, through no design of our own, have the effect of discouraging the establishment of strong families. Can there be a more urgent question on the domestic agenda than this? Do we really want to stand inattentively by as more and more women and children descend into poverty and dependency? Surely we do not. Surely Moynihan is right that we cannot have a healthy nation if its families are unhealthy, and that we must make it a matter of national policy to rescue them.