"Mr. Redford?" gulps a quavering-voice female undergrad in Zellerbach Theatre where, on a recent October evening, a capacity crowd of nearly a thousand previewed the actor-director's Lions for Lambs. Afterward, they pitched softball questions.

"Before all of us gathered here," the undergrad prefaces her query to the rakish actor up on stage, "I would like to say, you're a very sexy guy."

"And this is a very sexy school," says Redford, a ruggedly youthful septuagenarian, before gentling the conversation back to his film.

"We're good at engagement outside our country, but not so good within it," Redford says about his most political movie since All the President's Men, which came out in 1976, a decade before most of these Penn students were born.

Lions, a triptych starring Meryl Streep as a skeptical journalist, Tom Cruise as a U.S. senator selling his new military initiative in Afghanistan, and Redford as a professor prodding a passive student toward activism, is the filmmaker's challenge to the YouTube generation.

It indicts the media for not informing, students for not performing, elected officials for not leading, and the country for not educating its youth. All in 90 minutes.

"Get active!" the figure in jeans and cowboy boots exhorts the cheering crowd.

From the stage, flanked by actors Michael Peña and Andrew Garfield, who play his students in the film, Redford paraphrases the words of his character, professor Stephen Malley: "It is better to try and fail than to fail to try. Political and social change is going to come from you." The audience eats it up like idealism-infused popcorn.

"Fascinating," murmurs Eugene Numoo, a Penn senior from Ghana and a cinema studies major. "He made this movie for students just like us."

Just as fascinating is how Lions for Lambs reconciles the decades-old Redford Paradox. In it, for perhaps the first time in his movie career, the figure Redford plays on screen is as passionate, funny and garrulous as he is off-screen.

In life this most aloof of idols, famously "the man who does not engage," as his director-chum Sydney Pollack (The Way We Were, Out of Africa) put it, isn't as detached as his screen persona.

Since the 1960s, when he vaulted to stardom as the Sundance Kid opposite Paul Newman's Butch Cassidy, Redford has actively advanced an environmental agenda, founded the Sundance Institute to nurture film artists, and produced (and starred in) critiques of status quo politics such as The Candidate (1972) and President's Men.

No matter that in one film he played a Senate candidate and in the other the journalist who helps bring down the Nixon administration. No matter that the Oscar-winning filmmaker directed Ordinary People and Quiz Show, among many films about family secrets and lies. The image of him that persists is that of the elusive cowboy freeze-framed and backlit against the sunset. Is this our Redford Paradox - or his?

"Directors muscle me to be iconic," he says with an offhand shrug, reflecting upon why he is different, more himself, on screen in Lions.

It is the morning after the Penn lovefest and Redford - midway through a college tour that includes previewing Lions at Berkeley, the University of Chicago and Harvard - is cooling his heels in a Philadelphia hotel suite.

His glorious hair, the amber waves of grain, have faded to winter wheat. Still. Were he 51, the trim figure in the black shirt, jeans and reading glasses would look damn fine. At 71, his weathered, lived-in face bespeaks character more than age. As an adjective, sexy is not inaccurate. But it insufficiently captures this specimen of active mind and radiant health.

Redford has directed himself only once before, in The Horse Whisperer, delivering one of his patented cowboy-in-the-sunset roles. If, in Lions for Lambs, Redford the activist corresponds with Redford the actor for the first time, it is because, he says, "though I don't particularly like directing myself, I do trust myself."

And he trusts his political gut. Lions for Lambs feels like a summation of everything that Redford - actor, activist, entertainer, father and citizen - is thinking about his country.