Washington ? Many of America’s largest public careers have been those of presidents. Many, but by no means all. Chief Justice John Marshall was more consequential than all but two presidents — Washington and Lincoln. Among 20th-century public servants, Gen. George Marshall — whose many achievements included discerning the talents of a Col. Eisenhower — may have been second in importance only to Franklin Roosevelt. And no 20th-century public career was as many-faceted and involved so much prescience about as many matters as that of Daniel Patrick Moynihan, who died Wednesday at 76.

He was born in Tulsa but spent his formative years on Manhattan’s Lower East Side, from which he rose to Harvard’s faculty and the administrations of Presidents Kennedy, Johnson, Nixon and Ford, serving as, among other things, ambassador to India and the U.S. representative at the United Nations. Then four Senate terms. Along the way he wrote more books than some of his colleagues read, and became something that, like Atlantis, is rumored to have once existed but has not recently been seen — the Democratic Party’s mind.

His was the most penetrating political intellect to come from New York since Alexander Hamilton, who, like Moynihan, saw over the horizon of his time, anticipating the evolving possibilities and problems of a consolidated, urbanized, industrial nation. A liberal who did not flinch from the label, he reminded conservatives that the Constitution’s framers “had more thoughts about power than merely its limitation.”

But he was a liberal dismayed by what he called “the leakage of reality from American life.” When, in 1994, the Senate debated an education bill, Moynihan compared the legislation’s two quantifiable goals — a high school graduation rate of “at least 90 percent” by 2000, and American students “first in the world in mathematics and science” — to Soviet grain production quotas.

The Senate’s Sisyphus, Moynihan was forever pushing uphill a boulder of inconvenient data. A social scientist trained to distinguish correlation from causation, and a wit, Moynihan puckishly said that a crucial determinant of the quality of American schools is proximity to the Canadian border. The barb in his jest was this: High cognitive outputs correlate not with high per-pupil expenditures but with a high percentage of two-parent families. For that, there was the rough geographical correlation that caused Moynihan to suggest that states trying to improve their students’ test scores should move closer to Canada.

For calling attention, four decades ago, to the crisis of the African-American family — 26 percent of children were being born out of wedlock — he was denounced as a racist by lesser liberals. Today the percentage among all Americans is 33, among African-Americans 69, and family disintegration, meaning absent fathers, is recognized as the most powerful predictor of most social pathologies.

At the U.N., he witnessed that institution’s inanity (as in its debate about the threat to peace posed by U.S. forces in the Virgin Islands, at that time 14 Coast Guardsmen, one shotgun, one pistol) and its viciousness (the resolution condemning Zionism as racism). Striving to move America “from apology to opposition,” he faulted U.S. foreign policy elites as “decent people, utterly unprepared for their work.”

Their “common denominator, apart from an incapacity to deal with ideas, was a fear of making a scene, a form of good manners that is a kind of substitute for ideas.” Except they did have one idea, that “the behavior of other nations, especially the developing nations, was fundamentally a reaction to the far worse behavior of the United States.”

Moynihan carried Woodrow Wilson’s faith in international law, but he had what Wilson lacked — an understanding that ethnicity makes the world go ’round. And bleed. The persistence of this premodern sensibility defeats what Moynihan called “the liberal expectancy.” He meant the expectation that the world would become tranquil as ethnicity and religion became fading residues of mankind’s infancy.

Moynihan’s Senate campaigns were managed by as tough-minded and savvy a pol as New York’s rough-and-tumble democracy has ever produced, a person who also is a distinguished archeologist — his wife, Elizabeth. In his first campaign, in 1976, Moynihan’s opponent was the incumbent, James Buckley, who playfully referred to “Professor Moynihan” from Harvard. Moynihan exclaimed with mock indignation, “The mudslinging has begun!”

His last home was an apartment on Washington’s Pennsylvania Avenue. That “Avenue of Presidents” was transformed from tattiness to majesty and vibrancy by three decades of his deep reflection about, and persistent insistence on, proper architectural expressions of the Republic’s spiritedness and reasonableness, virtues made wonderfully vivid in the life of Daniel Patrick Moynihan.

George Will is a columnist for Washington Post Writers Group