In the strait-laced, strong-willed mind of Sister Aloysius, the principal of a Catholic elementary school, doubt makes her weak. It diminishes her faith. Worst of all, doubt would allow the evil that she knows is happening to continue.

But is this evil of priestly pedophilia, of which Sister Aloysius is absolutely certain, really occurring? And is the remedy she is hellbent on implementing the right one? And if she succeeds, what will that do to her?

Questions are at the heart of "DOUBT," the 2005 Pulitzer Prize and Tony Award-winning play by John Patrick Shanley that is having its Washington debut at the National Theatre in a two-week engagement ending March 25.

The 90-minute production, in which veteran stage actress Cherry Jones reprises her Tony-winning Broadway role as Sister Aloysius, whistles by like a fast-track train. You are still digesting the dramatic twists of one scene when the next begins. You side with the priest, then with the nun. You are certain you know the truth, then you're suddenly unsure. Even the stage set befuddles. Wasn't that statue of Jesus next to the window, not in front of it, in the last garden scene?

By the end of the production, you are where Shanley wants you to be: Pondering how the multi-facted reality that we call life can be lived without doubt.

The playwright, who met nuns like Sister Aloysius at his own grade school in the Bronx, calls his work a 'parable.' Like those stories found in the sacred scriptures of many faiths, it's not the facts that matter so much as their interpretation.

And although "DOUBT" revolves around a situation that evokes the recent clergy sex scandal in the Roman Catholic Church, Shanley raises questions about the larger context of our contemporary public discourse on all matters, including religion, politics and war.

"We are living in a courtroom culture…of extreme advocacy, of confrontation, of judgment, and of verdict…Communication has become a contest of wills," Shanley wrote in an essay about his play. "Maybe it's because deep down under the chatter we have come to a place where we know that we don't know…anything. But nobody's willing to say that."

Shanley, a former U.S. Marine, echoes what saints and scholars of deep religious conviction have concluded down through the ages: That doubt is no sin, and perhaps even necessary, for growing into a living faith. "It is Doubt (so often experienced initially as weakness) that changes things," Shanley wrote in the same essay. "When a man feels unsteady, when he falters, when hard-won knowledge evaporates before his eyes, he's on the verge of growth.

"Doubt requires more courage than conviction does, and more energy; because conviction is a resting place and doubt is infinite-it is a passionate exercise," he added. "We've got to learn to live with a full measure of uncertainty. There is no last word. That's the silence under the chatter of our time."

Dressed in green vestments, the amiable Father Brendan Flynn, played by Chris McGarry, opens the play with his sermon on doubt by asking, "What do you do when you're not sure?" Not to worry, adds the priest who also coaches the boy's basketball team, because "doubt can be a bond as firm as certainty."

His nemesis Sister Aloysius, who believes that a "restless mind" is "not a good thing" and who is universally feared by her students, valiantly deflects challenges to her rock-solid conviction that Flynn is a child molester. But even she recognizes that battling perceived evil sometimes requires compromise. "In pursuit of wrong-doing, one steps away from God," she notes. "Of course, there's a price."

And she will pay that price.

Playwright Shanley, who also wrote the Oscar-winning sceenplay for the 1987 movie "Moonstruck," has punctuated his deeply probing and beautifully scripted play with plenty of wit, offering moments of laughter to relieve the mounting tension between priest and nun.

All four characters in "DOUBT," who also include Sister James, played by Lisa Joyce, and Mrs. Muller, mother of the eighth-grader at the center of Sister Aloysius' concerns, portrayed by Caroline Stefanie Clay, move through dramatic, painful transitions during the performance.

The standing ovation given the cast by a rapt audience on opening night March 13 was well-deserved.

Caryle Murphy is a former Washington Post reporter who covered religion.