When Bradley Cooper appeared on Bravo's "Inside the Actors Studio" last year, he couldn't help but be nervous.

He was the first graduate of the studio's master's program to make it on the show. And he was returning in triumph, having starred in such films as "The Hangover" and "Limitless" and appeared on Broadway opposite Julia Roberts in "Three Days of Rain."

But he was also offering thanks to one of his teachers, Elizabeth Kemp.

"I was never able to relax in my life before," he said, acknowledging her in a voice constricted with emotion. "The most sacred experience I ever had was in [her class]. No question about it."

Kemp, the head of the studio's drama department, was equally gracious.

"I had learned a great lesson from a mentor, Elia Kazan: I only want to work with people who give everything they have to give and make their work the most important thing to them in their life," she said on the show.

"[Cooper] gave more than I think even he thought humanly possibly to give."

That's the kind of effort she expects from her students. It may not feel comfortable, and it's probably not glamorous. But it's the truth. And truth forces them to go places they didn't know they could go.

It's a two-way street. She prods them. She challenges them. She gives them an environment where they feel protected, and then she works to break down their defenses.

Mentoring can be instrumental to fostering creativity. We stand on the shoulders of giants, it is said, but those shoulders don't have to belong to innovators and geniuses. Sometimes they belong to unheralded people whose probing questions, thoughtful guidance and unadorned encouragement push us in new directions.

Their impact can be transformative: Kemp recalls one student who'd been typecast as a mousy, desperate character -- because that's how he saw his niche. She gave him an assignment to be a king in a particular scene. He found a new range as an actor -- and a new sense of himself.

"You help them grow into parts of themselves that they didn't even know they had," she says.

Kemp, 54, sits in an empty, dimly lit black-box theater at The Actors Studio's Midtown headquarters. She's a striking woman, with large blue eyes, full lips and a head of blond hair that looks like it has just emerged from the shower. At times her conversation threatens to float off into the mystical, with talk of connections and destinies, but there's a steel in her voice. She knows what she's doing. She's been in the game for more than 40 years.

She was once like her students: young, uncertain, a little scared. She had some moments of acting glory -- part of the original cast of the hit musical "The Best Little Whorehouse in Texas," roles in "L.A. Law" and "thirtysomething" -- and then hit a wall. It would change her life -- and the lives of other actors.

Good acting requires vulnerability, she observes, and often actors are their own worst critics. Her goal is to allow her students to trust themselves "just enough to take a chance, to be daring, to go into the unknown and discover. It's a very delicate balance."

Cooper can't praise Kemp highly enough.

"She made it safe," he says. "She made us realize that you have to use all of yourself. She just made it OK, OK to be yourself with all your faults and your fears and insecurities -- they were all brought out to the light and she insisted that you be vulnerable and put it all out there; there was no sort of faking."

Zones of comfort

There are subtle differences between teachers and mentors. The entrepreneur Steve Blank perhaps put it best when he observed that teachers and coaches impart knowledge and push students to discover specific lessons on their own, while mentors work in one-on-one relationships and present broader life lessons. In the "Star Wars" films, some management mentors suggest, Yoda is a coach, teaching Luke how to use the Force, and Obi-Wan Kenobi is a mentor, showing him what it means to be a Jedi knight -- and a man. One of Kemp's students prefers the term "mystogogue," an initiator into the sacred mysteries.

When the mentor-student relationship crystallizes, the potential for development is greatest. "By pushing yourself to those limits, you tap into resources unknown," says Kemp. "That's when the real growth occurs."

Kemp likes to create a comfort zone. Others -- including one of Kemp's mentors, Elia Kazan -- can be more pointed in their practice.

Kazan was recognized as a brilliant director; a generation of Method actors placed themselves in his hands. But he was also known for poking at their vulnerabilities as much as protecting them. As J.W. Williamson writes in "Hillbillyland," when Kazan directed Andy Griffith in "A Face in the Crowd," he discovered Griffith was sensitive about his poor Southern background. Just before rolling the camera, Kazan would whisper "white trash" to Griffith. Just the words would set him off.

Regardless of approach, good mentors always base their work on passion, says Kemp: "Not anger, not rage, not venom, but passion. And that's something I think that any mentor-guide would always share, is the passion."

Kazan would likely agree. "I am able to ... arouse [actors] to better work," he once wrote. "I have strong, even violent, feelings, and they are assets."

Students have to be willing to trust in their guides, says Craig Tanner, a Savannah, Georgia-based photographer who regularly runs creativity workshops. It's not easy: Many of his students arrive with expertise in one area and are resistant to becoming an apprentice in another.