Rick Foucheux as Freud, left, and Todd Scofield as Lewis. (Stan Barouh)

Sigmund Freud cracks five pretty good jokes in the first five minutes of “Freud’s Last Session,” Mark St. Germain’s easygoing two-character drama. St. Germain wants you to like Freud, even though he depicts the godfather of psychoanalysis as aggressive, mean and probably on his last legs. He’s 83, and oral cancer is ravaging his mouth. And it’s 1939, so World War II is revving up.

Why do we need to warm to this crank? Because he’s broaching one of the no-no topics, religion: The old atheist appears to be looking, one last time, for God. Why else would Freud have summoned C.S. Lewis — a famous Christian convert, on his way to writing “The Screwtape Letters” and “The Chronicles of Narnia” — to his office for what turns out to be about an hour-long theological debate?

Theater J hardly needs St. Germain’s gingerly approach to venture into matters of faith; that’s where this troupe lives. Yet even if the banter in this imaginary meeting is a little eager to please, there’s nothing wrong with the soothing tone of this show. Freud’s dyspeptic punch lines generate happy laughter in the audience, and as he is played by the wily Rick Foucheux, it’s almost a dirty pleasure to watch Sigmund voluptuously rolling a cigar between his lips.

The details are, what — divine? Director Serge Seiden, long of the Studio Theatre just a few blocks away, brings that troupe’s cool, near-surgical house style to this taut 80-minute production. Designer Deb Booth’s set is a tasteful, high-ceilinged room lined with leather-bound books and decorated with a formidable collection of gods and goddesses — maybe two dozen or so gathered as if for a séance on Freud’s desk. (Deb Thomas did the props.) Ivania Stack dresses the famous gentlemen in dueling three-piece suits, brown for Freud and light gray for Lewis.

The acting is likewise fine-grained, with Foucheux’s richly wound-up Freud as a frequently amusing counterpoint to Todd Scofield’s serene Lewis. Foucheux is a particularly good likeness as Freud — white beard, dark-rimmed glasses — and the analyst’s crabby manner is reflected in Foucheux’s sideways regard of Lewis.

Scofield, on the other hand, is superb as the polite guest, fielding Freud’s abrupt challenges with droll British wit and generally indulging the gruff Freud like a fond son pacifying an ailing father. Lewis gets punch lines, too, and it’s generally infectious when Scofield’s Lewis appears charmed by the whole situation.

The play’s complications include radio updates on the war, an air raid scare in which we realize that Lewis carries his own gas mask and horrific flare-ups of Freud’s oral cancer that are rendered with breathtaking accuracy by Seiden and Foucheux. Eventually, St. Germain peels beneath the surface and gets the characters to dig into the central question with passion.

“These are myths and fantasies,” Foucheux’s increasingly dismissive Freud rants about religious fables.

“But does that make them lies?” Scofield’s Lewis asks with profound wonderment.

St. Germain’s play isn’t after greatness; it’s not ferocious or dogged or deep. Yet it’s not simply earnest and slick, either, for Freud turns out to be a good vessel for the eternal questions. He’s ruthlessly logical and bitterly skeptical as he stares down a life that’s had lacerating disappointments.

Foucheux really burrows into this. The jokes come from darkness, and the complicated behavior comes from a heady mix of intellectual delight, titanic ego and the most primal kind of human fear.

As a play, “Freud’s Last Session” may glide along fairly easily, but Foucheux’s central performance has a magnificently unsettled edge.

‘Freud’s Last Session’

by Mark St. Germain. Directed by Serge Seiden. Lights, Dan Wagner; sound design, Eric Shimolenis. About 80 minutes. Through June 29 at Theater J, 1529 16th St. NW. Tickets $35-$65.Call 800-494-8497 or visit washingtondcjcc.org/center-for-arts/theater-j/.