Mel Packer pressed the bell and waited. A frail woman peered out from behind a storm door.

"We're just handing out information on the G-20 so folks know what it is," he said. The woman took the sheet of newsprint from his hand. She looked skeptical. He continued: "The city says it's good for us, but we don't think it is."

The woman glanced at Mr. Packer, balding and bespectacled in running shoes and shorts, a smile on his face and a small peace sign pinned to his sweatshirt. She cracked the door wider.

"Well, I don't think it is, either!" she said.

Across the street, Alex Bradley also knocked on doors and offered the same flier from a bundle under his arm.

They are two men of different generations -- Mr. Packer is 64, Mr. Bradley, 29 -- and different backgrounds. They walked the same hilly Greenfield street last week to push the same message: The global capitalism promoted by the G-20 doesn't work.

Both will take to the streets in protest when the world leaders and central bankers meet here this month, activists who have arrived at similar world views from their own separate paths.

Mr. Packer was an active trade unionist turned physician's assistant who found his ideologies as he found himself. Mr. Bradley was a high school student in Indiana, Pa., who said he was jarred by class struggles in his own family and never felt comfortable with the status quo.

Mr. Bradley is an anarchist; Mr. Packer is a "revolutionary socialist," who identifies with anarchists and has been working with them in opposition to the G-20.

Their titles alone put them among the most demonized of G-20 protesters, a contingent often associated with civil unrest and destruction.

But Mr. Bradley and Mr. Packer insist they are not out to smash storefronts and destroy the city. Rather, they see themselves as your neighbors who are fed up with a system they see as flawed beyond repair.

They drove to Greenfield together in Mr. Packer's Pontiac Vibe -- adorned in bumper stickers with messages like, "Politicians and diapers need to be changed, often for the same reason," and "If you're not outraged you're not paying attention."

To an elderly woman who answered her door with questions, Mr. Packer put his views on the G-20 plainly:

"What they do and the policies they set are the reason so many of my neighbors are unemployed."

As a physician's assistant practicing emergency medicine, Mr. Packer often lends an ear to people who have lost their jobs and can't afford health insurance. Listening to their plight renews his fight for change.

But he sensed the need for reform much earlier in life, growing up in Groton, Conn.

He left Groton at age 16, returned to get his high school diploma at 20 and then left again to study drama at Carnegie Mellon University and, later, work as a youth organizer in Wilkinsburg.

Along the way, Mr. Packer was active in a host of social and political movements: the civil rights movement, the anti-war movement and the anti-apartheid movement, to name a few. He has been with the Thomas Merton Center for many years.

"And I've loved every minute of it," he said.

Just as Mr. Packer became disturbed by the capitalist system at an early age, so did Mr. Bradley. The school year was spent in Indiana, Pa., with his middle-class father, and summers with his mother, who, he said, was very poor. The difference, he said, was jarring.

After high school, Mr. Bradley organized his first small protest when he and three friends stood in the snow outside an Exxon gas station in Indiana, angry that the company was still refusing to pay millions of dollars in damages after its Valdez tanker spilled more than 10 million gallons of crude oil into Alaska's Prince William Sound in an ecological disaster a decade earlier.

A police officer harassed the group, Mr. Bradley said. He was not discouraged, but he was angry.

He decided after high school that he couldn't travel the "normal career path of middle-class white people" so he moved to the West Coast and got involved in social movements. At 21, he declared himself an anarchist.

"My anarchism, at its root, is the struggle to decentralize power," he said. "Those who are impacted by decision-making should be making the decisions."

He was emboldened when 50,000 protesters descended on Seattle in 1999 during the gathering of the World Trade Organization. He traveled from anti-globalization protests and mobilizations from there on.

"There was an amazing energy in this country," that lasted until the Sept. 11, 2001, terrorist attacks, he said. After that, the fight for global justice shifted into an anti-war movement. Mr. Bradley moved back to Pittsburgh and became an activist here; he was among anti-war protesters who were pepper sprayed by police during a 2003 march in Frick Park. Since then he has been part of demonstrations and shared his experiences with other activists.

In July, Mr. Bradley led a class, Participating in Mass Action 101, inside the graffiti-covered walls of the Greater Pittsburgh Anarchist Collective's Garfield gathering space. A small group of experienced protesters and curious first-timers gathered around him.

As the group disbanded, he offered encouragement.

"You feeling good about the G-20? Cause I think we're going to rock it."