One of the great pleasures of living in London is that a friend can email you (in this case from Salamanca) and say: “Hey, did you know Clay Shirky, a world famous internet guru, is speaking at LSE in 60 minutes?—and you can drop everything, go, and be thrilled.

I knew about Shirky from having reviewed his book “Here Comes Everybody: How Change Happens When People Come Together” for the British Journal of General Practice (BJGP). His thesis is that when people are given new and easy ways to come together—through email, social networking sites, wikis, and the like—then remarkable and unexpected things happen. Through the new tools we can ascend the ladder of sharing, cooperating, and taking collective action, humbling professions, churches, and authoritarian governments as we go. It’s great stuff for us quasi-anarchists.

Sharky was in London to launch his new book “Cognitive Surplus: Creativity and Generosity in a Connected Age.” In his talk he argued that after 40 years of being largely consumers—of television, newspapers, magazines, and films—we now have the tools to use the creativity that is in all of us to have fun, produce free goods of real value, and potentially change the world.

His books are full of stories, and he began with the story of Sri Rem Sena, a Hindu fundamentalist who encouraged his followers to beat up Indian women in Bangalore who drank in pubs and lived Western style lives. Sri Rem Sena then announced that his followers would attack any woman seen in a pub on Valentine’s Day. How should women respond? It would be a brave woman who went to a pub on her own, but might there be other women who would join her? Before social networking sites it would have been hard, probably impossible, for the women to organise in time. As it was, women formed a Facebook group called “Consortium of Pub going, Loose and Forward Women” and urged members to send a pair of pink knickers to Sri Rem Sena. Through Facebook the women could come together, express their outrage, and find a creative and funny way to get back at their persecutor. Their numbers and campaign also meant that the authorities had to act, and Sri Rem Sena and followers were arrested on 13 February.

Shirky asked himself how big the creative surplus might be, and he started by calculating that Wikipedia has taken some 100 million hours to create over 10 years. That sounds like a lot, but Shirky also calculated that Americans spend about 200 billion hours a year watching television. Wikipedia could be produced in the time that Americans spend watching advertisements in a single year. There is a lot of cognitive surplus available, and small shifts might produce wonderful things. But it may take time: Shirky pointed out that pornography appeared almost immediately after the printing press was invented, whereas it took 150 years for the first scientific journal to appear.

We might use our cognitive surplus to produce fun sites like Lolcats , but, although lots of pictures of “cute cats” might produce pleasure, it isn’t going to change the world. Sharky, still fond of ladders, calls these “communal” sites and they are “everywhere.” Next up the ladder comes what he called “public” sites where a group of people produce a great public good for free. Only about two percent of the users of Wikipedia actually write much, but that’s enough people to produce something wonderful.

Higher still on the ladder are “civic” sites where people not only produce a valuable public good but actually change society. He quoted the example of PatientsLikeMe, where patients share detailed data about themselves in the hope not only that it can produce new knowledge but also that it can create social change, empowering patients relative to professionals, and help fix broken health care systems. Shirky quoted the Openness Philosophy of PatientsLike Me:

“Most healthcare websites have a Privacy Policy. Naturally, we do too. But at PatientsLikeMe, we’re more excited about our Openness Philosophy. It may sound counterintuitive, but it’s what drives our groundbreaking concept.

You see, we believe sharing your healthcare experiences and outcomes is good. Why? Because when patients share real-world data, collaboration on a global scale becomes possible. New treatments become possible. Most importantly, change becomes possible. At PatientsLikeMe, we are passionate about bringing people together for a greater purpose: speeding up the pace of research and fixing a broken healthcare system.”

PatientsLikeMe, by encouraging patients to share data about themselves, is trying to reverse a strong cultural tradition of keeping such information private, and, said Shirky, “I don’t know if they’ll succeed.” But he emphasized that it’s the cultural and social changes rather than the tools that really make a difference. The tools are a means to the end, and social contracts are very powerful.

He illustrated the power of social contracts by describing research conducted by two Israeli psychologists in a Haifa day care centre and published in the Journal of Legal Studies. The psychologists were studying the impact of fines, and in one group of day care centres they introduced a fine if parents were late in picking up their children. Counterintuitively, the number of parents picking up their children late increased compared with a control group. Presumably the parents felt released from their social contract with the teachers and thought that they could simply pay for the privilege of being late. The fines were then removed, but there were still more parents picking up their children late in the centres where the fines had been imposed. The social contract had been broken.

Inevitably when I heard this story I thought of the consultant contract, that turned a social contract where most consultants worked more hours than they were contracted to do because of their professional commitment to patients, into a financial contract that led to consultants being paid more but doing less. But Shirky’s point was that social and cultural contracts can be more powerful than money. We won’t need to be paid to use our cognitive surplus for good ends.

Which makes me wonder why I’m writing this blog—and in danger of missing the start of the Spain-Portugal game? I’m not being paid, and it’s taken me about an hour—longer than usual because I’ve been searching for stuff on the web. It must be that my cognitive surplus is overflowing.

Richard Smith was the editor of the BMJ until 2004.