Paging Dr. Freud

"It's funny you should say that. It was actually this very day," Rayner says by phone from the Berkshires, where he'll star in the world premiere of Mark St. Germain's "Freud's Last Session," starting next Wednesday at Barrington Stage Company in Pittsfield.

"I had been, overnight, working on some ideas for adjustments to the character to make him more austere than I have been playing him in rehearsal," Rayner says. "And this morning I came in with that idea in mind, and I was given a pair of glasses that were very Freud-like. And putting them on and using that new thought, it really clicked with me. I thought for the first time, oh, this is him."

Under the direction of Tyler Marchant, Rayner plays Freud at the end of his life. The great psychoanalytic thinker is in London at the start of World War II, dying of oral cancer. And in St. Germain's speculative vision, Freud invites a young Oxford don named C.S. Lewis to drop by for a chat. Of course their conversation develops into a heady debate about the nature of God and man.

"It can go from quite high ideas to basically two children shouting rude things at each other," Rayner says with a chuckle. "There are moments of intimacy between them, moments of humor between them, moments almost of hatred between them. What's fun about it is, in the time we have on the stage, it's really a roller coaster from beginning to end."

St. Germain's play was inspired by Dr. Armand Nicholi's book "The Question of God" and a single reference to Freud receiving a visit from an unnamed young Oxford don shortly before his suicide. St. Germain pictured Freud, an atheist, probing the Christian beliefs of Lewis, a former atheist.

"It's not a debate, it's not two people standing behind a podium," the playwright says. "It's really an encounter between two men. I think Freud would very much like to prove himself totally right and send Lewis out the door in five minutes. But instead, the two become very intrigued by each other."

So what's it like being the man who argues with Sigmund Freud?

"It's interesting playing this kind of iconic guy against this other iconic guy," says Mark H. Dold, who plays Lewis. "But I can be slightly easier on myself because there's not as much known about C.S. Lewis as Freud. There's not the cigar or the eyeglasses or the couch or the goatee. People think about 'The Lion, the Witch, and the Wardrobe,' but that's also Lewis much later in his life. I play Lewis as a relatively young man."

Through June 28. Tickets: $25-$39. Preview tickets for June 10-11, $15. Pay What You Can Night is June 12 at 7:30 p.m., minimum $5 cash at door. 413-236-8888, www.barringtonstageco.org