In the case of the elusive David H. Souter, there are many clues and one large mystery.

Since the obscure judge's Supreme Court nomination Monday, published accounts about him are strikingly similar. They tally with what one hears privately from people who have known him for years, in one case dating back to his time at Oxford.

The Souter that emerges is bright, honorable and reserved. A loner, but not lonely, and not without humor, he's invariably described as an independent man, never married, who lives alone and keeps his own counsel. By temperament and cast of mind he's conservative -- but that doesn't necessarily mean "conservative" by today's inexact definition. He's a judicial minimalist, it is agreed, and would not be expected to lead, or join, an expansion of government powers from the bench. Yet he does not appear to be someone who automatically takes a narrow, punitive view on large social questions, though much remains to be learned about his views in this critical area. At this point, we simply don't know enough.

Most of all, he's a Yankee, a throwback, it seems, to an almost vanished small-town New England of decades past.

Here stands the conjunction between what we know about him -- and don't.

I was intrigued to learn, for instance, that as a Harvard undergraduate Souter was fascinated by the life and example of that quintessential great New Englander, Mr. Justice Oliver Wendell Holmes. So much so, according to a New York Times account, that Souter "wrote his senior honor's thesis about Holmes's judicial positivism."

Yet -- and here is the mystery -- while Holmes was a great intellectual force he was also a great human being of passion and conviction, tempered by a range of life experiences that shaped his thinking and responses from the bench. We do not know the same about the enigmatic Judge Souter. We know about his withdrawn life. We know almost nothing about how he thinks and feels. The distinction is vital.

As Catherine Dinker Bowen wrote of Holmes in her superlative biography, "Yankee From Olympus":

"Holmes's greatness lay most of all in his manner of meeting life. He had a genius for living, a genius for finding himself wholly, using himself wholly. He loved life and believed in it. 'If I were dying,' he wrote at 80-odd to a young man, 'my last words would be, Have faith and pursue the unknown end.' For him the act of learning was always an adventure. Passionately, until the morning of his death, he pursued knowledge. 'To know is not less than to feel,' he said. 'A valid idea is worth a regiment any day.' "

To Holmes, life was to be lived, and learned from. He was shaped, and changed, by his personal experiences, central among them his Civil War service. Three times he was grievously wounded. First were wounds in the chest and stomach at the Battle of Ball's Bluff, across the Potomac near Leesburg. He was only 20 at the time.

Two years later, on the bloody field at Antietam, Capt. Holmes was found lying on the ground severely shot through the neck. He heard an army surgeon stand above him and say, "I've no time to waste on dead men."

Later, when starry-eyed fellow Bostonians came to talk to the hero, they were offended by what he said. "War?" Holmes repeated coldly, his gray eyes remote. "War is an organized bore."

His visitors left shaking their heads. "Captain Holmes used to be so agreeable," Bowen quotes one of them as saying. "How changed he is. Is it possible that he is going over to the radicals?"

Still later, upon recovering, Holmes was badly wounded again when shrapnel tore ligament and tendons in his ankle at the Battle of Chancellorsville. From these experiences, Holmes concluded that people were divided into two kinds: external and internal. Internal ones considered ideas more interesting than things. Holmes placed himself among those who acted.

"Through our great good fortune," he later wrote, "in our youth our hearts were touched with fire. It was given us to learn at the outset that life is a profound and passionate thing. . . . "

A person's one and only success, he added, was "to bring to his work a mighty heart."

No doubt Judge Souter possesses the intellectual capacity for the Supreme Court. The question is whether he possesses "a mighty heart." Does he have a wise and tolerant view of life that can lift him into the ranks of great justices like Holmes? With so elusive, if not reclusive, a person, and so critical an appointment for the next generation of Americans, those conducting his confirmation hearings face an even far more formidable task than usual in helping us to know and understand him.