In TRAVELER IN THE DARK, playwright Marsha Norman creates a world where BIG concepts dominate: Faith clashes with Doubt, Youth seeks to triumph over Mortality, Innocence is shattered, and Knowledge is modern man's crown of thorns. But the concepts are too big, with too many of them vying for the audience's attention. As a result, the characters and audience are left to flounder in a sea of unanswered questions and un-satisfying answers.

Traveler is broadly ambitious; Norman has dared to expand since her most recent success, 'Night Mother, characterized by its tightly-defined unity of time, space and action. ('Night Mother, like Traveler, also premiered at the American Repertory Theatre, and it won the Pulitzer Prize for Best Drama last spring.) Four characters inhabit the world of Traveler, the action takes place outdoors, and the conflicts are multiple and complex. But Traveler lacks 'Night Mother's greatest strength: believability.

In the playwright's words, Traveler is "about a brilliant surgeon, whose intelligence is not enough to save him. Samuel Carter seems to have it all--a beautiful wife, a bright little boy and a dazzling career--but he is a traveler in the dark." Unfortunately, both the bitterness and the self-righteousness of this 40-year-old cynic prove unbearable. Sam preaches his doctrine of atheism and the supremacy of intelligence with more offensive zeal than the loudest Moral Majority proselytizer. Told for so long about his brilliance, Sam comes to believe that he does, in fact, know the truth about everything.

Sam Waterston's performance as Sam Carter further exacerbates the problems inherent in creating this character. For the first half of the play, he is a big baby, throwing temper tantrums and quarrelling with his wife and father in front of his young son. Later, when we learn the reason for his aberrant behavior, the excuse seems insufficient. Waterston remains on one level throughout his portrayal of this man who has clearly reached the end of his rope: his rope: his strained hysterics rarely vary.

Sam's father Everett (Hume Cronyn) opitomizes Organized Religion, and since Sam is a modern Everyman, God the Father and God Sam's father inevitably get mixed up. Fortunately, Cronyn doesn't pay much attention to the heavy-handed symbolism and manages to create the play's only believable character. He ends the first act with an oddly powerful prayer and unfortunately gets bogged down when he has to repeat the trick at the end of the play.

Like father Everett, wife Glory (Phyllis Somerville) and son Stephen (Damion Scheller) have to endure Sam's tiresome tirades. But while they help to highlight some aspects of Sam's character, they never become real characters in their own right. Empty-headed and beautiful, compassionate and forgiving, Glory remains inexplicably unperturbed when her husband announces his intention to leave her and take their son with him. She goes on smiling, fixing lunch and loving her dear Sam.

The character of Stephen suffers from the same lack of definition. Playwright (and audience) can't figure out if he's five or 15: one minute he asks idiotic questions about the meaning of "Humpty Dumpty," and the next he lectures his father on the nature of moral responsibility. Scheller carries off some of the more moving moments of the second act with admirable aplomb, but it seems a crime to saddle a 13-year-old actor with such a large-and inconsistent--role.

NORMAN REVEALS a bewildering predilection for nursery rhymes in Traveler-this theme is carried over to Heidi Landesman's set, which features a gingerbread house and a fanciful Mother Goose garden. Sam quotes and analyzes nursery rhymes at great length, and the result is a tedious and heavy-handed string of tired metaphors describing the aforementioned Big Concepts. The funny one-liners which permeate the play also lose their effect after two repetitive hours.

Norman must get annoyed when critics compare Traveler in the Dark to 'Night Mother, especially when the comparison is unfavorable, But she set very high standards for herself with 'Night Mother, and we can only hope that she will meet these standards again with her next play. Ted Osius