TED recognized that no session on the subject of evil is complete without Stanford psychology professor emeritus  Philip Zimbardo. In 1971, he conducted a famous experiment in which ordinary people were cast as guards and prisoners in a mock jail setting; many of the "guards" began to act brutally, while many "prisoners" showed signs of emotional trauma.

This year's TED Prize winners, Cambridge physicist Neil Turok, author Dave Eggers, and lecturer and writer Karen Armstrong will address the question "How Can We Change the World?" (For more on their efforts, see their profiles: Turok, Eggers, Armstrong.)

On Friday, novelist Amy Tan will join an origami artist, a product designer, a visual effects supervisor, and a composer to answer the question "How Do We Create?"

Another session, "What's Out There?", will feature ideas from a mix of professionals, including an ocean explorer, an animal behaviorist, and a futurist. Nassim Nicholas Taleb, a scholar of randomness, and Walter Isaacson, former editor of Time magazine, will speculate about what tomorrow will bring.

And for "What Stirs Us?", TED invited a photography editor, a novelist, an anthropologist, and the conductor of the Boston Philharmonic Orchestra to shed some light.

On Saturday, the closing day of the conference, Al Gore will be among those answering the question "How Dare We Be Optimistic?" Gore gave his climate-change presentation to attendees of the 2006 TED conference, and this year the Nobel Prize-winning former vice president will discuss a new topic that hasn't yet been disclosed.

The TED conference will surely end on a positive note, with the question "What Is the Point?" being answered by the musician Bob Geldof and the social psychologist Jonathan Haidt, author of The Happiness Hypothesis.

Attendees will close out the four-day think-fest with a barbecue lunch on the shore in Monterey. It will be a bittersweet beach party, since it's the last year the conference will be held here. TED announced that, starting next year, the conference will move down the California coast to Long Beach.

But don't expect a bigger venue to make it any easier for just anyone with $6,000 and a burning curiosity to attend. Its organizers plan to invite only 100 more guests next year, even though the facility seats more than 3,000.

See Portfolio.com's full coverage of the 2008 TED Conference