It’s hard to believe it’s been 20 years since Doubt: A Parable first appeared Off-Broadway at Manhattan Theater Club and then transferred to Broadway winning the Tony, Drama Desk, Outer Critics, NY Drama Critics Awards and the Pulitzer Prize. John Patrick Shanley’s compact and powerful morality play pitting a determined nun against a charismatic priest she suspects of sexual misconduct still shakes and shatters. Scott Ellis’ revival for Roundabout Theater Company is as sturdy and upsetting as Doug Hughes’ original and Shanley’s self-directed 2008 film version. This is especially impressive considering Amy Ryan stepped into the lead of Sister Aloysius and had only a few weeks of rehearsal when Tyne Daly had to withdraw for medical reasons.

The plot is concise and tightly drawn. The setting is a Bronx Catholic middle school in 1964. The extremely conservative principal Sister Aloysius (she doesn’t even like her students to use ball-point pens or to waste their time with art or dance) suspects the popular, modern-thinking priest Father Flynn (a subtle and complex Liev Schreiber) of engaging in an “improper” relationship with the school’s only African-American student. She has no direct evidence, but based on observations from the boy’s teacher Sister James (a wonderfully sympathetic Zoe Kazan) and other details, Sister Aloysius is dead set on removing Flynn from her school and the parish.

The drama derives from that lack of clear-cut evidence. Is Sister Aloysius an accurate judge of character or a judgmental bigot? Is Father Flynn a forward-looking progressive or a sly deceiver? Ellis stages their confrontations with economy and strength, with David Rockwell’s revolving detailed set and Kenneth Posner’s moody lighting appropriately setting the scene. In addition to Ryan, Schreiber and Kazan’s pitch-perfect performances, Quincy Tyler Bernstine adds dimensions of complexity and nuance as the student’s conflicted mother.

If there are any caveats to the exemplary production, it’s that Schreiber is a little too convincing in his denials of guilt. Without revealing too much of Shanley’s clever plot turns, towards the end of the play, Father Flynn’s genial veneer cracks and we are left with ambiguity. In the original production, Brian F. O’Byrne added more layers to Flynn. He was charming and initially likable, but also manipulative and slippery (In his first encounter with Sister Aloysius, he sits behind her desk, attempting to usurp her authority.) Schreiber is too endearing and non-threatening, so the final outcome is not as many-shaded. Despite this flaw, Doubt remains a probing, thought-provoking examination of the chasm between certainty and questioning in how we conduct our lives.

Like Doubt, Itamar Moses’ new play The Ally at the Public Theater, offers no comfortable, clear-cut resolutions to the difficult questions it poses. It also presents many varying and articulate responses to its central question and allows the audience to decide the best outcome—if any. The play does have a plethora of long speeches and it can sometimes resemble a debate rather than a drama. The characters can occasionally seem like representatives of their espoused beliefs rather than flesh-and-blood people. But the talk is so detailed and stimulating, Ally’s flaws pale in comparison to its strengths. With a passionate yet never overplaying cast and understated direction from Lila Neugebauer, Ally is among the strongest, most politically conscious works currently playing on or Off-Broadway.

Moses examines numerous issues of social import but the central one involves the state of Israel and its policy towards the Palestinians. Set in a contemporary college campus in New York, The Ally asks how far one should go in the name of supporting persecuted minorities even when you disagree with their actions in order to gain equity. Writing professor Asaf (a thoughtful, funny and intense Josh Radnor) is asked to sign a radical progressive manifesto by Baron, one of his African-America students (Elijah Jones in a strong turn displaying contained anger and questing intellect), whose cousin has been killed at the hands of the police. One of the many paragraphs in the document calls Israel’s policy towards Gaza and the West Bank apartheid and uses the phrase genocide to describe their Palestinian policy.

It so happens the author of the document, Nakia (a blazing Cherise Boothe) is Asaf’s former girlfriend and his wife, the Korean-American Gwen (Joy Osmanski making the most of a relatively brief role), works for the university in pushing through a controversial housing project. In addition, Asaf is soon drawn into a hot-button campus conflict over freedom of speech. All these plot tracks clash in a powerful five-sided symphony of political discord—this is the heart of the play. Asaf, Nakia and Baron are joined by two students representing radical-left young American Jews (quirky Madeline Weinstein) and displaced, frustrated Palestinians (shattering Michael Khalid Karadsheh) as opinions, data, and passions fly. It’s stimulating, exciting theater.

As with Doubt, Ally has its flaws. There is an additional character speaking for the Israeli side (a searing Ben Rosenfield) who has an individual scene with Asaf. Though Rosenfeld delivers a fine honest reading of the character, he feels inserted in for balance since Asaf makes the same points later.

Lael Jellinek’s economic set, Reza Behjat’s subtle lighting, and Sarita Fellows’ understated costumes create a subdue environment for this fiery play. The time is described as September and early October of 2023, just before the vicious Hamas attacks and Israel’s causing response. The Ally would have been ever more incendiary if the setting were just a few weeks later. As it is, Moses’ work challenges and discomfits as much as Shanley’s continues to two decades after its initial run.

Doubt: A Parable: March 7—April 21. Roundabout Theater Company at the Todd Haimes Theater, 227 W. 42nd St., NYC. Running time: 90 mins. with no intermission. roundabouttheatre.org.

The Ally: Feb. 27—April 7. Public Theater, 425 Lafayette St., NYC. Running time: two hours and 40 mins. including intermission. publictheater.org.