Eugene Jarecki began by asking people ‘ politicians, military experts, moms ‘ a question: Why does the United States go to war?

The answers aren’t pretty. His documentary “Why We Fight” tells us that America fights because it’s profitable. It fights because rich white men use war for power. It fights because we’re stuck in a military-centered matrix and cannot see a way out.

The ideas, arguably, aren’t new. But Jarecki’s documentary is powerful not in its dark vision but in its moments of light.

There are too few of them. But Jarecki, 36, continues a kind of optimism in his own discussion ‘ with Jon Stewart on “The Daily Show,” with his students at Brown University and last month, with A&E.

In each instance he calls on young people in particular to learn from films like his and make change. But he’s not calling on them because they can’t pull themselves away from their PlayStations long enough to read a newspaper. He’s calling on them because he thinks they’re smart. He thinks they’re already learning about these issues and already making change.

“I spend a lot of time on college campuses,” Jarecki said. “And I’m extremely inspired by what I see there.”

As a visiting senior fellow at Brown University’s Watson Institute, Jarecki teaches international studies. Sure, he’s serious about this stuff now. But back in his days at Princeton, he wasn’t so politically active.

“By and large I was far too uninvolved in the world around me,” he said. “I think at the time there was a greater myth of American prosperity.”

Now that myth, Jarecki and his film say, is coming undone. Jarecki and his crew stopped in more than 30 states to talk with people about why they think the country goes to war. People’s first answer, Jarecki said, was “freedom.” But after he pressed them, he found that they said far more interesting things. Some people spit back thoughts on corporate greed. Some people weren’t angry but were, instead, unsure.

Of course, it’s a tricky question with a problematic answer. If every person says “freedom,” is the society that governs them truly free? And if people give all sorts of reasons ‘ from Lockheed Martin to cultural imperialism ‘ then a country is in disrepair.

“When you’ve lost national unity, the country has lost its most important line of defense,” Jarecki said. “It’s lost the willingness of its people to die for it.”

Jarecki sees national defense as more than bombs. He cannot separate national security from health care, from infrastructure, from education.

His documentary uses a speech from President Dwight D. Eisenhower to further the same thought. In the farewell address of his presidency, Eisenhower, a Republican and former general, warns the country about a growing “military industrial complex.” He’s worried, he says, that the country’s new focus on military will starve the government’s other responsibilities.

Jarecki has watched this prediction come true. He sees Eisenhower’s address as “genius,” and quotes it practically in its entirety in the course of the interview. But, each time, he must explain how what Ike predicted has not only come to pass, but gotten worse.

“Corruption is so amok that everyday people have their belief in the country challenged,” he said.

Jarecki features one such everyday person in his film. Wilton Sekzer, a New York City cop, wants the name of his dead son written on one of the bombs dropped in Iraq. His son died in the attacks of Sept. 11, 2001, and he’s angry about it. He wants someone ‘ an entire people ‘ punished.

Through the course of the film we witness a metamorphosis. Sekzer turns from a vengeful war hawk into a confused, hurt man who thinks his patriotism was hijacked by the Bush administration’s lies.

When Jarecki interviewed Sekzer, he had no idea he would witness such a moving moment of clarity.

“The film’s surprise is my surprise,” he said.

In that moment, Jarecki and his film gain greater power than a down-on-military film could have. He shows a conscious, thinking public considering these issues. At times, that public might be the minority. At times, it might not be heard.

But these things take time, he said. People are pushing in the right direction. It just might take a while for their shove to actually move things.

“People cannot lose hope. The human desire for greater clarity and a more sustainable world ‘ that’s worth dying for,” Jarecki said. “That’s worth living for. And that’s worth fighting for.”