By VINCENT J. CANNATO

In March 1965, a young political appointee in the Labor Department named Daniel Patrick Moynihan wrote a report warning of high levels of out-of-wedlock births in the black community. “The Negro Family: The Case for National Action,” as the report was officially titled, noted that nearly a quarter of all black children were born out of wedlock, a ratio that had been rising since the end of World War II. Such a trend, Mr. Moynihan warned, could deepen black poverty rates and lead to a “tangle of pathologies.”

The Moynihan Report, as it came to be known, informed a major presidential address by Lyndon Johnson, unleashed a firestorm of criticism and began four decades of debate over the connection between family life and poverty.

Now James T. Patterson, a professor emeritus at Brown University, has written a concise and judicious account of Mr. Moynihan’s political career, the report he made famous and the policy debates that the report inspired. This is a story not just about Mr. Moynihan but also about E. Franklin Frazier, James Q. Wilson, Christopher Jencks, William Julius Wilson and other scholars and commentators who have examined the connections between marriage, race and poverty. “Freedom Is Not Enough” is written in an engaging style that makes these debates come alive again and that reminds us of their continuing importance.

Mr. Moynihan took a lot of heat over his report, some of it brought on by his own tart rhetoric but much of it by the passions of the times: Black America in the 1960s was in no mood to be lectured at by a white government official. The Moynihan Report’s focus on illegitimacy was thought to deflect attention from white racism. In fact, the term “blaming the victim” comes from an attack on Mr. Moynihan that was written by a white liberal critic.

Mr. Patterson, though, is an admirer of Mr. Moynihan’s. He seeks to defend Mr. Moynihan’s ideas both from his enemies in the 1960s and from later critics who portrayed him as a self-aggrandizing blowhard. Mr. Patterson sees Mr. Moynihan as a “committed liberal” who believed that “unemployment was the major source of instability within poor families” and that “government could and should act to improve their chances in life.” It is certainly true that Mr. Moynihan was a child of the New Deal. One of his early ideas was to re-establish twice-a-day mail service to increase civil-service jobs for black males. To many liberals, the Moynihan Report seemed a clarion call for more federal programs to help repair the black family and strengthen inner-city communities.

The phrase “freedom is not enough” comes from LBJ’s 1965 speech at Howard University, partly written by Mr. Moynihan himself. Johnson called not just for equality of opportunity for black Americans but for equality of result. Slavery and racism had done terrible damage, he said; the government would need to step in and actively improve conditions in the black community—with jobs, decent housing and safer playgrounds, among much else. The speech was a high-water mark for activist liberalism.

Yet the problem of black poverty, as we know too well, was not so easily solved. One of the charts in the Moynihan Report showed that, by the early 1960s, inner-city welfare rates and unemployment rates were moving in opposite directions: Government subsidy for black single mothers was needed even when there was work to be had for black males. In short, poverty persisted even in good economic times. Clearly cultural changes were taking place, and economics alone could not explain the problem or solve it.

Mr. Moynihan was a conventional liberal Democrat after his election to the U.S. Senate in 1976 but hardly a firebrand for activist government. If anything he had become skeptical of government programs, like other “neoconservatives” of his generation, citing social science to show how so many such programs had failed. Unfortunately, as Mr. Moynihan noted in a 2002 speech, social science had its limits. Most lamentably it could not (in Mr. Patterson’s paraphrase) “explain fully the massive changes affecting family life in the western world.”

Whatever its causes, illegitimacy has proved to be among the most vexing aspects of modern society, especially in black communities. Ever since the Moynihan Report it has been argued that more job opportunities could help strengthen family life in the inner city. But better jobs depend on a decent education, and educational success depends in part on a stable home environment and a steady household income. A high rate of illegitimacy thus perpetuates the conditions that bring it about in the first place, creating a cycle of poverty.

In recent decades there has been progress of course; the black middle class has grown substantially. But inter-generational poverty continues in many inner-city communities. As for out-of-wedlock births, the problem has worsened and widened. In 2008, the black out-of-wedlock birth rate stood at 72.3%, more than three times the rate when Mr. Moynihan compiled his report. The white out-of-wedlock birth rate in 2008 was 28.6%, higher than the 1965 rate for blacks that had so alarmed Mr. Moynihan. (The rate for Hispanics is 52.5%.)

Clearly we are witnessing cultural changes that now go beyond the black family and even beyond the U.S.; Western Europe has also seen an increase in out-of-wedlock births. Mr. Patterson still clings to the hopes expressed by Lyndon Johnson, even if he is skeptical of the solutions that have been proposed since Mr. Moynihan sounded the alarm. Two generations of research and political quarreling have put us no closer to finding an answer to the problem of family breakdown.

Mr. Cannato is the author of “American Passage: The History of Ellis Island,” just out in paperback from HarperPerennial.