(FORTUNE Magazine) – True or false: "There is one and only one social responsibility of business--to use its resources and engage in activities designed to increase its profits so long as it stays within the rules of the game."

Them's fightin' words today even more than when they were written nearly 40 years ago by Nobel Prize-winning economist Milton Friedman. The great debate over business' responsibility to society, which bubbled in the '60s and '70s, is exploding now, with protesters from Seattle to Jakarta to Quebec City marching, chanting, breaking windows, overturning cars.

What's really happening behind all the hubbub? Two new and significant changes, so let's cut through the handwringing and pontificating that surround this issue. Ignore the protesters who are labor unionists in disguise, worried about losing their jobs to poorer people but claiming a nobler purpose; and ignore the rabid Marxists trying to feel young again. You're left with a core of mostly intelligent, articulate, sincere activists who worry the world will become a worse place with the historic falling of barriers to trade, capital flow, and information.

I've met lots of these activists. I always ask them the same question: Why should companies spend the money to do what you want--improve the environment, make suppliers offer better working conditions to employees, support human rights in countries where they operate? And the answer is invariably the same: Companies should do those things out of self-interest. What? You mean to maximize long-term profitability? Absolutely, comes the answer.

That's the first change. Back in the '70s, an outfit called Campaign GM wanted General Motors to abandon its focus on profitability and improve the environment, among other things. Today Campaign GM's philosophical successors claim they can help GM make more money. And no, I don't think they're being disingenuous. The capitalist revolution of the past 20 years was real. Plenty of profit haters are still out there, but even among corporate-citizenship activists, they're on the fringe.

The second big change, far more significant, is that companies today are doing more of what the activists want than they ever have done before, and it's not because they're being socially responsible. It's because they're listening to the markets. If it seems surprising that as the world has become more virulently capitalist, it has also become more concerned about the environment, child labor, and human rights--well, that's what makes life interesting. Some would argue that the world's rising prosperity has helped make room for those issues on the mainstream agenda.

The fact is that today consumers care about those things more than ever. A substantial number now base buying decisions on who made their Nike shoes or where Exxon Mobil got its gasoline or what McDonald's does with its paper waste. The trend is hardly universal--plenty of people still just want the lowest price--but it's utterly clear. You've seen it yourself, probably in your own family.

At least as important as consumers' caring, employees care. One trend in business is that employees, especially the best young employees, want a sense of purpose in their work. We all want a sense of purpose in our lives, but in the past we didn't demand it from our jobs. Now workers increasingly do. They want to know that what they do at work is good and right in some large sense. Since most companies are in a desperate war for talent, they'd better be able to make that case.

Consumers care and employees care. That means equity markets care. And that means CEOs care.

Thus, for example, we see Ford and BP, formerly monsters in the view of social-responsibility types, working hard to greenify themselves. Some of what they've done is real and some is window dressing, but the fact is that Ford Chairman William Clay Ford got a standing ovation from the Coalition for Environmentally Responsible Economies, and BP CEO John Browne gets plenty of media calls seeking his comment on all kinds of enviro-matters. That would have been unimaginable a few years ago.

Read Friedman's line about "the one and only one social responsibility of business" to advocates for corporate social responsibility, as I have done, and they laugh indulgently: We don't really have to bother refuting such caveman views, do we? But the truth is that most companies are behaving just the way Friedman wants them to.

And though many of the activists don't yet realize it, that's the best news they've had in years.