One might usefully distinguish, in recent American history, between figures whose notoriety exceeded their merits and those of whom the reverse was true. In any such division, Grenville Clark -- lawyer, fellow of Harvard, architect of the First World War officer training camps and of the World War II Selective Service system, philanthropist, world federalist -- would be a strong candidate for list No. 2.

That his name recognition isn't high -- this sprightly biography will help, but won't make him a household word -- tells us something of how elite power once was exercised in the United States and of the essential frivolity of fame.

What it says about power is that in Grenville Clark's heyday -- the mid-1920s to, say, the mid-1950s -- it was often inversely proportional to its visibility.

A ninth-generation Manhattanite (born in 1882), of proud and established lineage, Clark was that rarity, a genuine American patrician. With his keen sense of public responsibility -- Dunne calls it "Calvinist," though Clark was christened an Episcopalian and died a Unitarian -- Clark might have followed his early idol, Theodore Roosevelt, into politics.

Instead, he took what was outwardly a quieter track. After Harvard (college and law school) he joined the New York City bar. In 1909 he and Elihu Root Jr. organized one of the premier Manhattan law firms, known during his most active years as Root, Clark, Howland & Ballantine. There he made quite a lot of money advising and defending corporate clients, taking time off to oppose, in the best upper-crust fashion, the people's parkways that Robert Moses planned to ease the way of plebeians to his Long Island beaches. (Moses prevailed; he usually did.)

No doubt Clark's money-making remains of interest in Manhattan law circles (where beginners are now paid $70,000 a year), but it is the least interesting or significant fact about his career. It was what he was, not what he earned, that defined him -- perhaps the only indelible mark of the patrician American.

And Grenville Clark usually had a cause, discreetly pursued through the mediation of powerful friends, in timely law review articles or pamphlets, and occasionally in letters to the editor of The New York Times.

What differentiated Clark's ideas from routine do-gooding was the care with which he thought them through. Thus when it seemed probable that the United States would be drawn into World War I, the young Clark and a number of his young professional friends organized a committee, with the advice of "Colonel" Theodore Roosevelt. They hatched the idea of what soon became the Plattsburg officer training camps. A quarter-century later, still in the forefront of "preparedness," Clark helped plan and write the Selective Service law. As well, he and his law school friend and classmate, Felix Frankfurter, seem to have persuaded their friend Franklin Delano Roosevelt to call Henry L. Stimson from retirement to be secretary of war.

Dunne's larger theme, indeed, is how Clark evolved from social and political conservatism in liberal directions -- so liberal, in fact, that the late 1940s saw him siding with those who blamed the United States and the Truman administration about equally with the Russians for the deterioration of wartime collaboration and the rise of the Cold War. No doubt his views were distinguishable from those of Henry A. Wallace; but that was the flavor. It was not sympathy with the Soviet system; it was his grasp of the history underlying Russia's sense of beleaguerment. His views would not be fashionable in Reaganite circles.

But Clark, after working as an unpaid volunteer assistant to Stimson for most of the war, had been commanded by the secretary to "go home and think of ways to avoid World War III." Clark's answer was world federalism. Though sometimes identified as a dreamy utopian scheme, world federalism was, like all Clark's ideas, carefully thought through and solidly based, in fact, on American experience with federalism under law.

It goes without saying that Grenville Clark deplored and opposed the Red-baiting climate of the early 1950s, especially as expressed in loyalty oaths for teachers. Like Adlai Stevenson and Dean Acheson, two fellow patricians, he was considerate of, though not credulous about, Alger Hiss when Hiss got into trouble. In the 1960s, he developed a strong interest in civil rights and not only gave generously to the NAACP but inspired others to do so as well.

When you add to all this that he was devotedly married to a handsome and well-born New England woman named Fanny, and that he was physically imposing and powerful, he sounds almost like a character imagined by Louis Auchincloss, differing only in actually believing the ruling-class code of rectitude and responsibility he professed.

Perhaps, indeed, it is true to say that such figures are now more likely to be found in books than in the flesh, and certainly less likely than half a century ago to devote so many otherwise "billable" hours to public duties, or to succeed in them.

More "democratic" we are than the country that produced Grenville Clark a century ago, which is as Clark himself wished it to be. Whether the per capita quantum of social responsibility is as high as it was in the more candidly elitist world in which he moved is another question. It is a question that Gerald Dunne's very readable book implicitly poses but does not answer.

The reviewer is a syndicated columnist for The Washington Post Writers Group.