THE REAL THING, Pioneer Theatre Company, Simmons Pioneer Memorial Theatre, through April 3, 581-6961. Running time: 2 hours, 20 minutes (one intermission).

Maybe the Monkees' "I'm a Believer" had it wrong. Maybe love is only true in fairy tales.

Or maybe Tom Stoppard has it wrong in "The Real Thing." His protagonist, who just happens to be a playwright, says that carnal knowledge is always true; it's the real knowledge.

Certainly, Stoppard wants us to ponder this. Early on, his lovers know "the insularity of passion." Without insularity, without exclusivity, can their love even last until the end of Act II?

Stoppard gives us a dozen complicated questions to ponder in this play. For balance, he also gives us the simple lyrics from rock songs. And, with Charles Morey directing, the Pioneer Memorial production of this Tony-winning script challenges us and succeeds on several levels.

First, the actor who plays Henry, Paul DeBoy, is great. He makes the most of all the witty lines and banter he is given in this script. Second, the staging is nice. (Scenic design by James Wolk; costumes, Brenda Van der Weil; lights, Karl Haas; sound, Joe Payne.) The set is stark. A series of panels serve as walls and they rotate, and as the actors revolve on and off the stage, the audience is forced to think about the interchangeability of the lovers.

One difficulty: The other actors were all hard to hear at one point or another on opening night. Maybe it was the accents. Certainly these are accomplished actors, easily equal to the rich roles Stoppard has written.

Max Robinson plays a sadly innocent husband. Joyce Cohen is Charlotte, a woman who can take care of herself whether she is married or not. Jurian Hughes is Annie, who can't find the right words to say to the writer she loves.

Sensitivity rating: The subject is adultery. There is some swearing; also smoking onstage.