SCRATCH A psychiatrist, and underneath you find a writer. In the case of Robert Coles, you find maybe four or five writers.

There's the essayist of The New Republic and The New Yorker , where parts of this work first appeared. There's the social historian of the Children of Crisis books. There's the poet of A Festering Sweetness , and there's the children's writer of Dead End School . There's also the literary critic of Irony in the Mind's Life and William Carlos Williams: The Knack of Survival in America .

For his thirtieth book (how does he do it all?) the psychiatrist and professor at Harvard Medical School wears his hat as literary critic and gives us a knowing, if almost adulatory, study of the writings of Walker Percy. Another literary physician, but one who hasn't practiced for around 30 years, Percy is the author of four novels (The Moviegoer, The Last Gentleman, Love in the Ruins, Lancelot ) and a collection of essays on language, existentialism, and neo-Catholic philosophy called The Message in the Bottle .

Reading Percy marked a turning point in Coles's life. In the summer of 1960, Coles had been discharged from the Air Force in Mississippi and was trying to decide whether to study the lives of black children caught between oppression and social change, or, perhaps, play it safe with medicine. He came upon The Moviegoer , Percy's existentialist novel about a listless New Orleans stockbroker who avoids life by attending movies.

"Walker Percy's novel gave hope to me, helped me feel stronger at a critical time, when I was somewhat lost, confused, vulnerable, and, it seemed, drifting badly."

He adopted Percy then as a mentor, and Coles himself has subsequently become something of a Christian existentialist, judging from his latest book and the essays of The Mind's Fate .

"I have relied upon Dr. Percy's ideas constantly," Coles writes, "to the point that I can scarcely imagine how I would have thought about either my own life or the lives of the children, parents, teachers I have met (in order to write Children of Crisis ), were he to have decided, long ago, to keep his important and instructive thoughts to himself."

There are, of course, almost as many varieties of existentialism as there are of squash. Coles weighs them carefully, educating us in the subtleties of their quests for meaning in life, before placing Percy to the right of both Camus, with his ultimate philosophical question of suicide, and Sartre, with his "nothingness as the prime reality." Coles settles Percy in the less painful Christian shades of Gabriel Marcel's "communion of selves" where he can engage in Soren Kierkegaard's less fatal maneuvers of "rotation" and "repetition."

Detached but not quite coming apart, Percy's heroes vacillate betwen boredom and inaction -- often comically and ironically -- and grow ever more anxious as they come closer to others. They are existentialist ideas become human, says Coles, as he matches them with their cousins in Kafka's Amerika or Dostoevsky's The Brother's Karamazov . They are walking recluses. In their world, as Hegel said, everything has been figured out, except how to live. They suffer from a malaise or a wasted passion -- the terms come from both Sartre and Percy -- to know what cannot be known about the meaning of life. Unable to perceive any grand drama, except a promised death, they excuse themselves from even the sideshow. And no commitment means no danger.

During some 80,000 words spent tracking these noncommittal heroes who have fled to the movies, booze, or into someone else's life, Coles shows us the Christian patina of Percy's novels. The commitment-dodgers drop their self-protective shields and stop their evasion tactics when they learn to acknowledge themselves through a significant other person. And in the best existentialist fashion this other person is close to the void -- a suicidal lover, a priest, a fatally ill boy, an old woman near death.

Because Percy is an American and a Southerner as well as an existentialist, his novels digest the whole glorious claptrap of our advanced civilization -- clothes, games, sex, Cougars and collard greens -- as his pilgrims and castaways wonder when to dare freedom, how to take, as Coles says, "a step that is our own rather than yet another gesture of compliance." Percy writes down-home philosophical fiction.

To show that Percy's novels are chasing something alive, Coles often quotes reports from troubled and directionless souls in the South or on assembly lines. These are too long, strangely literate, and make it difficult to know where Percy's ideas end and Coles's inferences start.

For a psychiatrist Coles passes up many a probe. Within two years of one another both of Percy's parents died -- his father a suicide, his mother killed in an automobile accident. Percy himself faced death when he contracted tuberculosis as a resident pathologist at Bellevue in New York, and he escaped or quit medicine as a result. Percy has never had to work for a living; he converted to Catholicism at the age of 31, a few months after being married in a Southern Baptist church.

All this gets relatively little attention. It would have had, I'd guess, enormous effects on an author's attitude toward life and his perception of human motive. One has the feeling Dr. Coles and Dr. Percy haven't talked much about it, staying on safer subjects like Heidegger's noticing that "man struggles against enormous difficulties to find himself."

It also would have been helpful to know where Coles sees Percy's limits. The novels are not all perfect. Do Percy's existential insights really apply to all of us? Bantu tribesmen as well as literary intellectuals? It's not an accident that existentialism rose out of industrialized societies.

So Coles's search of Walker Percy's American search is less complete than one would wish.

But he establishes beyond question that Percy isn't just another Southern novelist. He is pursuing a world, not a region. Like his European colleagues in letters, he has found in the novel or drama "a suitable, flexible, and suggestive mode of moral, psychological, and social inquiry." Coles' book also organizes and analyzes literary existentialism extremely well, and he connects it to psychoanalytic thought in ways that seem new.

As always in a work by Robert Coles, one feels a warm, compassionate intelligence. Even as he practices some existentialist evasions himself, he is smarter and more generous than most people you'll read this year. He looks to praise, not condemn, and knows how to find what he looks for.

Whoever writes about Walker Percy again will have to read Walker Percy: An American Search . Including, of course, between the lines.