Leigh was born in Manchester into a socialist Zionist background, not unlike that of Rachel (Laura Esterman) and Danny (Richard Masur), the parents of an assimilated, secular North London family, who appear untroubled by questions of faith. While their conversations are peppered with Yiddishisms, any suggestion of their heritage is absent from their middle-class environment, crisply rendered in set designer Derek McLane's comfortably conservative living room.

Being British, Rachel and Danny are less single-mindedly pro-Israel than a similar American couple might be. Their willingness to turn an objective, critical eye on the Israeli/Palestinian conflict identifies them as Europeans but also underscores their disillusionment with what happened to the early idealism of the Zionist movement. They have raised their children to be open-minded, questioning people, so the discovery that 28-year-old son Josh (Jordan Gelber) has taken up Orthodox Judaism comes almost as a violation.

Leigh and director Scott Elliott slyly drop this revelation by showing Josh sneaking furtively around the darkened room, seemingly preparing to shoot up, but in fact laying tefillin.

The emergence of the family conflict dominates the play's first act. Josh has been unmotivated and unemployed since graduating with honors in mathematics; his embrace of something so arguably irrational as religion is viewed as mishegas by his father and opinionated grandfather, Dave (Merwin Goldsmith), with concern from his mother and bemusement from his sister Tammy (Natasha Lyonne), a globe-trotting interpreter caught up in leftist causes.

Backgrounded by lengthy political discussions that sweep from the Middle East to the U.S. and Latin America to Tony Blair's New Labour Britain (action takes place between July 2004 and September 2005), act one unfolds in short scenes punctuated by blackouts and bursts of jaunty music by the Klezmatics. As much as Leigh's diligence can be appreciated in sketching the liberal family's engagement in world issues, the stop-start structure does little to further character development and the conversation often drifts toward banality.

As always, though, Leigh's unhurried groundwork pays off when tension erupts in the second act, drawing parallels between global conflicts and the intractable war zones within families that may be belabored but are effective nonetheless.

Bringing a surge of vitality, expanded perspective and humor to the family unit are Tammy's Israeli boyfriend Tzachi (Yuval Boim) and Rachel's monstrously self-absorbed younger sister Michelle (Cindy Katz), who has been out of touch for the past 11 years and now wonders why no-one appears moved by her ostentatious displays of grief over her estranged mother's death three months earlier.

While Michelle is a borderline caricature in keeping with the vague sitcom feel of the setup, she provides Leigh with sharp opportunities to desecrate the sacred altar of family, particularly when using pitilessly straight-talking Dave as a mouthpiece.

Leigh's signature creative process -- developing his scripts via extended workshops during which the actors contribute to dialogue and character development through improvisations based around a handful of concrete elements -- bears fruit cumulatively rather than from the start. His characters are a shouty, often abrasive bunch, but as their nerves become increasingly frayed and they drop their guards, the writer's compassion makes the family frictions more immediate.

This is the fifth collaboration between New Group a.d. Elliott and the playwright, and the director's ease with Leigh's naturally conversational dialogue helps steer the play through some of its drier patches. While the actors here don't have the close-knit advantage of being in on the gestation that the original London cast had, the prickly bonds of a familiarity that's both comforting and grating are evident throughout the solid ensemble.

But what resonates most about "Two Thousand Years" is its vigorous sense of identity and its stealth-like optimism, apparent especially in an elegantly understated coda scene. Rachel, Danny and Dave may have distanced themselves from their faith, but they are inextricably Jewish in every aspect of how they act, think and talk. However, by fostering an active connection to their roots, it's the younger generation that is most centered.

For all Rachel's talk about the failure of the kibbutz as a utopian society, Tzachi seems a healthy product of that environment while also representing socially engaged Tammy's link to Israel and a significant source of her glowing serenity. And for all his dour defensiveness, Josh's act of religious rebellion marks a bold step toward achieving a sense of himself that has eluded him since college.

Even wryly antireligious Dave acknowledges the validity of Josh's pursuit of deeper meaning in his life. "At least he's found something," he says to his discontented daughter Michelle. "What have you found?"
 
Sets, Derek McLane; costumes, Mimi O'Donnell; lighting, Jason Lyons; original music, the Klezmatics; sound, Ken Travis; dialect coach, Stephen Gabis; production stage manager, Valerie A. Peterson. Opened Feb. 7, 2008. Reviewed Feb. 2. Running time: 2 HOURS, 15 MIN.