Young people have an almost biological destiny to be hopeful.

Grassroots organizations grow stronger to the extent that their leaders go out and engage more people. It's all about building as broad a base as you can. The right seems to get it much more about being committed and cooperating with other committed people, and going out and evangelizing. There is an evangelical spirit in their movement that is a great strength to them. And there hasn't been a whole lot of that on the liberal side.

The Sierra Club is a blend of the recreational folks and public-policy folks. Both currents are pretty strong in there -- it's a source of tension in the organization, but a creative tension. That's one of their unique strengths: They offer a way for people to enjoy nature, but also make the bridge over to the kinds of public policy required to preserve the opportunity to enjoy nature.

They reach into a constituency that is important for the overall success of a progressive movement in America. It's only a part of that movement -- it's middle class and more educated -- but it plays a very important role. The club challenges those people to turn their values into political action and community action.

In South Africa, where HIV-positive children are often shunned, we have an HIV-positive Muppet to teach children to be friendly with children with HIV. But they use local actors. And it's not always a street. Sometimes it's 'Sesame Plaza,' or 'Sesame Tree.'

I was a TV producer at a noncommercial station, and we were producing some good documentaries - on Head Start, on poverty. But I was struck by the children, and the damage that poverty was doing to them. I didn't think filming them was helping much, so I wondered how we could use TV for them, to teach them.