The Berkeley Repertory Theatre, dedicated to provocation, has produced an excellent version of Nina Raine's Tribes. It might appear to be a play about an "issue," deafness in this instance. But it is a drama about the subject of drama since Greek tragedy, which is our inability to communicate with one another. Whether you speak or sign, you are likely to leave the show with something to say about it.

The set up is ingenious. The two protagonists, Billy and Sylvia, are mirror images who perforce fall for each other.

The opening scene introduces a family so engrossed with themselves and their words that they would be despicable if they were not hilarious. The unopinionated life is not worth living: This clan is so garrulous, by their scale the merely talkative may as well be mute. The father is a literary critic; the mother, a would-be mystery novelist; the eldest son, a graduate student stalled on his thesis in linguistics; the daughter, a novice opera singer appearing in English translations; and the youngest son, Billy, seemingly sullen at the dinner table until it is revealed he is alone among them in being deaf. Consistent with the father's bombastic if not dictatorial tendencies, he has protected his progeny from what he denigrates as the cult of big-D Deafness, meaning sign language and everything else it symbolizes.

The moving force arrives in the form of Sylvia. She is a CODA, Child of Deaf Adults. While she is hearing, she has inherited a progressive loss of the sense. Unlike Billy, however, she is fluent in American Sign Language (ASL) and moves within Deaf Culture. (The play is set in England, but it is ASL rather than British Sign Language in use here. The discrepancy will be overlooked by 99 percent of the audience, who likely do not know that ASL is related to French Sign Language and not British Sign Language.)

Even as his adult siblings boomerang back into the family home, to the chagrin of their elders, Billy moves out. Sylvia becomes his guide to an independence he never even dreamed of. Ironically, the first job he finds depends on his skill as a lip-reader. He becomes some sort of law enforcement expert witness explicating surveillance videos of criminal activity (for which there is no soundtrack).

The plot avoids being didactic, because Raine has given herself an advantage. Her characters are naturally argumentative. They are the type of people who would use the word "discourse." Their debates are as realistic as any debate among academics.

The moral of the story at a superficial level is that it is not deafness which prevents an individual from leading a life complete; it is the lack of communications. The cause of the problem is less a physical handicap than a societal disregard -- in this instance, a familial fault. Everyone loves Billy, but they love him as a mascot.

Most deaf people are born to hearing parents. Billy's family wants to hold on to him; they do not want him to leave, even in the literal sense of preferring he stay at home. Hearing people may not appreciate the same desire on the part of deaf parents. They also may well want to have children who resemble them. Raine has explained she was inspired by the controversy over such a case, to write her script.

Yet matters are more complex. Deaf culture is not spared. It is described from a distance as insular and paranoid, displaying its own hierarchy that inverts the mainstream (to be deaf born of deaf parents is the best, to be hearing is the worst). All that is glimpsed of it comes from Sylvia as an interpreter. She would rather be hearing, because she has grown up so.

The conclusion resolves this conflict of assimilation with one of many potential outcomes. While Billy turns out to be imperfect, perhaps he should be forgiven for what is disclosed as his failing: from his perspective, his choices all follow from what has come before. Sylvia cannot stay; she must adjust to her own new identity.

The least sympathetic character is the imperious patriarch -- said not to be modeled on the author's well-known forebear. He denies the possibilities for the deaf to be equal, and the assertion makes itself true. For someone who has always been deaf, the absence of the ability to hear is no more a disability than for those of us who are hearing but lack, say, a sense of sonar. We miss nothing that we care about. We would dismiss anyone who claimed superiority for possessing such a skill.

He has it backwards with his fear that the deaf who are proud to have formed a community thereby define themselves by it. Among those who all share such a characteristic, it ceases to be essential and no longer distinguishes anybody. People are better able to assert themselves as individuals.

The Berkeley Rep has done what is right in casting. They selected a deaf actor, James Caverly, as Billy, rather than engage in what has been dubbed "disability drag," the equivalent of blackface. Caverly previously inhabited the role in Boston and Washington, D.C.

In Tribes, the deaf come off better than the hearing, though nobody escapes their sense of self-importance. The story works because it uses the particular to show the universal. To the contrary of the Anna Karenina principle (happy families are all alike; every unhappy family is unhappy in its own way), Tribes suggests that there are no happy families and unhappy families are unhappy because of an innate inability to understand one another. We are all the same in our solipsism. Nobody understands anybody else.