Digital media have made creating and disseminating text, sound, and images cheap, easy and global. The bulk of publicly available media is now created by people who understand little of the professional standards and practices for media.

Instead, these amateurs produce endless streams of mediocrity, eroding cultural norms about quality and acceptability, and leading to increasingly alarmed predictions of incipient chaos and intellectual collapse.

But of course, that's what always happens. Every increase in freedom to create or consume media, from paperback books to YouTube, alarms people accustomed to the restrictions of the old system, convincing them that the new media will make young people stupid. This fear dates back to at least the invention of movable type.

As Gutenberg's press spread through Europe, the Bible was translated into local languages, enabling direct encounters with the text; this was accompanied by a flood of contemporary literature, most of it mediocre. Vulgar versions of the Bible and distracting secular writings fueled religious unrest and civic confusion, leading to claims that the printing press, if not controlled, would lead to chaos and the dismemberment of European intellectual life.

These claims were, of course, correct. Print fueled the Protestant Reformation, which did indeed destroy the Church's pan-European hold on intellectual life. What the 16th-century foes of print didn't imagine—couldn't imagine—was what followed: We built new norms around newly abundant and contemporary literature. Novels, newspapers, scientific journals, the separation of fiction and non-fiction, all of these innovations were created during the collapse of the scribal system, and all had the effect of increasing, rather than decreasing, the intellectual range and output of society.

To take a famous example, the essential insight of the scientific revolution was peer review, the idea that science was a collaborative effort that included the feedback and participation of others. Peer review was a cultural institution that took the printing press for granted as a means of distributing research quickly and widely, but added the kind of cultural constraints that made it valuable.

We are living through a similar explosion of publishing capability today, where digital media link over a billion people into the same network. This linking together in turn lets us tap our cognitive surplus, the trillion hours a year of free time the educated population of the planet has to spend doing things they care about. In the 20th century, the bulk of that time was spent watching television, but our cognitive surplus is so enormous that diverting even a tiny fraction of time from consumption to participation can create enormous positive effects.

Wikipedia took the idea of peer review and applied it to volunteers on a global scale, becoming the most important English reference work in less than 10 years. Yet the cumulative time devoted to creating Wikipedia, something like 100 million hours of human thought, is expended by Americans every weekend, just watching ads. It only takes a fractional shift in the direction of participation to create remarkable new educational resources.

Similarly, open source software, created without managerial control of the workers or ownership of the product, has been critical to the spread of the Web. Searches for everything from supernovae to prime numbers now happen as giant, distributed efforts. Ushahidi, the Kenyan crisis mapping tool invented in 2008, now aggregates citizen reports about crises the world over. PatientsLikeMe, a website designed to accelerate medical research by getting patients to publicly share their health information, has assembled a larger group of sufferers of Lou Gehrig's disease than any pharmaceutical agency in history, by appealing to the shared sense of seeking medical progress.

Of course, not everything people care about is a high-minded project. Whenever media become more abundant, average quality falls quickly, while new institutional models for quality arise slowly. Today we have The World's Funniest Home Videos running 24/7 on YouTube, while the potentially world-changing uses of cognitive surplus are still early and special cases.

That always happens too. In the history of print, we got erotic novels 100 years before we got scientific journals, and complaints about distraction have been rampant; no less a beneficiary of the printing press than Martin Luther complained, "The multitude of books is a great evil. There is no measure of limit to this fever for writing." Edgar Allan Poe, writing during another surge in publishing, concluded, "The enormous multiplication of books in every branch of knowledge is one of the greatest evils of this age; since it presents one of the most serious obstacles to the acquisition of correct information."

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