Africa doesn't get much play in the media. On the other hand, Brad Pitt ducks and dives to stay out of the media. This is why Hollywood's most desirable man spent Friday preparing for a new role: Brad Pitt, trade expert.

Pitt takes this business seriously. Black suit, black notebook. A profound, concentrated look. Impressively neat handwriting.

Across the table, Steve Radelet from the Center for Global Development is running through the standard arguments on trade: comparative advantage, infant industry protection, import substitution. Pitt keeps writing it all down, looking like the journalism major he once was. Then he asks a question.

"If I could interrupt. . . . "

Interrupt? Millions dream of being, ah, interrupted by this idol.

"If I could interrupt, isn't the argument more about worker rights?"

Radelet explains that trade-oriented firms in the poor world treat workers better than factories that produce for the local market.

"Shouldn't the argument be, what's not good enough for us is not good enough for them?" Pitt persists. "In the movie business, we can't burn toxic things when we film in the United States. So we go to Morocco and burn all the rubber tires we like when we're doing action scenes."

Hmm. The economist concedes that the actor has a point: Morocco's air quality matters. But if a poor country wants to attract Hollywood's business, maybe it has a right to relax environmental standards?

A little later, somebody remarks that the poor don't earn much from exports because the value is all in Western brands. Why do people pay for this ethereal thing called brand?

"I'm a brand," Pitt interjects. "I ask myself this question."

The meeting goes on for an hour and a half, and there's no respite afterward. A former U.S. trade negotiator arrives to brief Pitt; later there are trade specialists from the AFL-CIO and Friends of the Earth, then two West African cotton farmers. By the end of the day, Pitt's still taking careful notes. He looks deep into the farmers' eyes and promises to get their message to the public.

That could really change stuff. In the run-up to the Group of Eight summit in Scotland last summer, Pitt got Africa onto Diane Sawyer's "Primetime Live" for a full hour by offering himself up for an interview. His effort reinforced those of the rock stars who staged the "Live 8" concerts just before the summit, and it embarrassed the rich world into promising more aid. The hope is to repeat that trick on behalf of the Doha round of trade talks, which currently are stuck. France leads a pack of rich nations that refuse to cut the farm protectionism that harms poor nations.

Trade could use this sort of backing. Business groups that once lobbied energetically for freer trade have lost some of their passion, because past trade deals have already removed many of the barriers that bugged them. So now Pitt and his allies must ride to the rescue. DATA, the activist outfit that sponsored Pitt's tutorials, has convinced development groups that traditionally ignored trade that they should sign on to a pro-Doha platform. American religious leaders, who have long campaigned for Third World debt relief, are planning to use a meeting with Secretary of State Condoleezza Rice next week to lobby for trade liberalization. Rice's visitors will speak for some 80 million Americans, and Brad Pitt alone has almost as many fans. Sect appeal plus sex appeal becomes the new trade lobby.

And yet there are some worries. Campaigning for trade is more complex than campaigning for aid, because trade creates losers as well as winners. Some poor countries currently benefit from preferential access to rich markets -- preferences that would disappear if these markets were opened to everyone. Other poor countries are net food importers, so cutting rich-world farm subsidies and driving up food prices would hurt them. Still other poor countries stand to gain from trade, but some of their people would get hurt: If India cuts its rice tariffs, urban consumers will gain but rice farmers will suffer. Then there are the environmental and worker-rights questions that Pitt raised in his tutorials. As the idol put it Friday, trade can be a little "fuzzy."

This may cause the activists to flinch from real trade advocacy. Rather than pushing for the deepest liberalization possible, they may push for seemingly more appealing goals: side deals on commodities that are important to Africa, such as cotton, or a deal that puts the onus on rich countries to open their markets without demanding that developing countries reciprocate. But rich countries aren't likely to make deep concessions on cotton outside the context of a broader trade deal that includes prizes for them. And much of the benefit to poor countries from freer trade would come from cuts in their own tariffs.

If you are going to be for trade, you have to accept that there'll be winners and losers, always remembering that the gains will be bigger. According to the World Bank, complete trade liberalization would enrich developing countries to the tune of $135 billion a year, more than these countries receive annually in aid and much, much more than they stand to gain from debt relief. If Pitt and his friends feel fuzzy about trade, that's the number to remember.