Theater may have evolved out of religious ritual, but at the late part of this century it's taken a few steps back toward its origins with a turn to the confessional. The latest trend involves playwrights spilling their histories from a well-lighted stage. So now we're vouchsafed the news that Jean-Claude van Itallie likes the idea of being fucked, but doesn't act on it because it "hurts." This outpouring of carnal revelation comes late in the dramatist-turned- vaudeville-song-and-dance-man's War, Sex, and Dreams, during which he relays, without seeming very comfortable about it, his peregrinations since he was born in 1936 to two European Jews. Old enough at the time only to remember certain details of the family flight from the Anschluss, he does recall that his naughtiness troubled an adoring mother and stern father. "I don't know how to be a good boy," he laments. He repeats that sort of intermittently touching moment when, at his mother's deathbed, he mimes what was an unspoken parental bylaw: speak, hear, and see no evil. The puckish Downtown veteran discusses his bout with fame when America Hurrah opened and, in particular, recalls a heady evening spent with Leonard Bernstein and Jerome Robbins that provides a glimpse into the people- collecting proclivities of the rapaciously talented. He also delves into his sexual awakening with, for one, his Harvard roommate. He opens, incidentally, on an anecdote about his dinner-party meeting with man-of-the-week Elia Kazan. It's not that van Itallie's autobiography lacks interest how could it, since he was in at the birth of Off-Broadway? It's that the boards aren't the hospitable format. As to his singing among others, "Que Reste-t-il de Nos Amours" and "Shall We Dance?" it's an indulgence best saved for the shower.