Like most scholars, I was skeptical about Wikipedia when Jimmy Wales first launched the site back in 2001. The notion that unvetted volunteers cooperatively contributing to an online encyclopedia might produce a reference work of any real value seemed at best dubious—and, more likely, laughably absurd. Surely it would be riddled with errors. Surely its coverage would be ridiculously patchy. Surely it would lack the breadth, depth, and nuance of more traditional reference works like the venerable Encyclopedia Britannica.

My initial skepticism is now proof of how little I understood what Jimmy Wales grasped far better than I. Wikipedia exploded from an initial 20,000 articles in 18 languages during its first year to more than 19 million articles in 270 languages (3.8 million of them in English alone) written or edited by 82,000 active contributors. Whatever reservations one might still have about its overall quality, I don't believe there's much doubt that Wikipedia is the largest, most comprehensive, copiously detailed, stunningly useful encyclopedia in all of human history.

I myself use it on a daily basis, and am pretty sure most of my colleagues and students do too even if they won't admit it. It consistently ranks just behind Facebook, Google, YouTube, and Yahoo among the most visited sites on the Web, with 400 million unique visitors and 6 billion individual page views per month during 2011. For a small nonprofit organization with three dozen paid employees to achieve this kind of prominence against corporations with vastly more capital makes its achievement all the more astonishing.

More to the point, though, Wikipedia is today the gateway through which millions of people now seek access to knowledge which not long ago was only available using tools constructed and maintained by professional scholars. Whatever the reference tools we consulted—dictionaries, almanacs, encyclopedias, books of quotations, finding aids, bibliographies—we did so because their contents had been carefully scrutinized by professionals with appropriate scholarly training.

No longer. Wikipedia and its kin have changed all that, and those of us who inhabit the world of scholarship need to ponder the ongoing role of professional authority when traditional disciplines can no longer maintain the kind of intellectual monopolies that their members once took for granted. No one needs a PhD in a subject, or even a baccalaureate major, to contribute or modify Wikipedia entries. Although the wide-open Wiki world sometimes harbors howling errors, even outright fraud, the overall quality of Wikipedia content is remarkably good. If one's goal is quick consultation for information one can check in other ways, or a brief orientation to an unfamiliar topic, then it's hard to imagine a more serviceable tool than Wikipedia. I even have an app that downloads to my iPhone the entire English-language contents of the site—over four gigabytes—so I always have it at my fingertips even when I'm offline.

Don't get me wrong. I'm not saying that any encyclopedia entry is a substitute for the much deeper, richer, more integrated knowledge that has always been the goal of good scholarship. Like every teacher, I caution my students not to rely on encyclopedias when doing serious research. And despite the claims made by a controversial report in Nature back in December 2005 that scientific entries in Wikipedia and Encyclopedia Britannica were surprisingly comparable in their proclivity for errors, I generally agree with those who defend Britannica for its traditional excellence in scholarly nuance and quality of writing when compared with its online rival.

I'm not extolling the virtues of Wikipedia because I regard it as the epitome of scholarly synthesis. Of course not. But the contrast with Encyclopedia Britannica does point to the changing nature of scholarly authority in a digital age. Britannica was first published in Edinburgh in 1768, and promoted itself from 1824 forward (with the publication of the Supplement to the fourth, fifth, and sixth editions) by commissioning signed contributions by eminent scholars. The famous 11th edition, published in 1910–11, is widely regarded as the most distinguished of all. Historians who contributed entries included J. B. Bury on the Roman Empire, H. M. Chadwick on Anglo-Saxon England, James Harvey Robinson on the Reformation, A. F. Pollard on Tudor England, and Frederick Jackson Turner on U.S. history. Just a few of the historians who have contributed to editions since then include Jacques Barzun, Clayborne Carson, Linda Colley, Joseph Ellis, Eric Foner, John Keegan, James Lockhart, William McNeill, James McPherson, Allan Nevins, Jaroslav Pelikan, Henri Pirenne, Jonathan Spence, Romila Thapar, Arnold Toynbee, Sean Wilentz, and Gordon Wood. The scholarly authority of names like these helped make Britannica the gold standard of English-language encyclopedias for more than a century and a half.

Yet Wikipedia has now triumphed with no such reliance on named scholarly experts. Like much on the internet created in a mechanically templated multiauthored environment, it is at its best when presenting simple descriptive summaries and linear narratives broken down into predictable taxonomic subsections that can be composed and edited in modular units. Long, complicated interpretations exploring subtly interacting historical causes in carefully contextualized analyses or beautifully flowing narratives—these one will never find on Wikipedia.

What one will find is a breadth and intellectual scope that put even the largest traditional encyclopedias to shame. Unsurprisingly, Wikipedia blows away most competitors for topics involving scientific or technical information, not only because it attracts volunteers especially knowledgeable in these areas, but because it can give such topics all the space they need and revise them literally by the minute. Compare Wikipedia with Britannica on "Fermat's Last Theorem" and you'll see what I mean. On topics of current interest, including many environmental subjects central to my own work, Wikipedia has a nimbleness that even newspapers have trouble matching. Its entry on Hurricane Katrina, for instance, already filled many screens while the storm was still raging over New Orleans. (Britannica, in contrast, still offers only seven short paragraphs on the subject.) Even controversial topics that are famous for generating warring submissions by opposing sides often do a remarkably good job of migrating toward shared middle ground. Compare Wikipedia's entry on "abortion" or "abortion debate" with Britannica's and ask yourself which does a better job.

Perhaps most importantly, Wikipedia provides an online home for people interested in histories long marginalized by the traditional academy. The old boundary between antiquarianism and professional history collapses in an online universe where people who love a particular subject can compile and share endless historical resources for its study in ways never possible before. Amateur genealogists have enabled the creation of document databases that quantitative historians of the 1960s could only fantasize. In my own field of environmental history, I've long told students that gardens and cooking, which have only recently begun to attract the academic attention they deserve, have been studied for generations by serious antiquarians and amateur scholars (many of them women) whose interests were marginalized by a male-dominated academy. In the wikified world of the Web, it's no longer possible to police these boundaries of academic respectability, and we may all be the better for it if only we can embrace this new openness without losing the commitment to rigor that the best amateurs and professionals have always shared more than the professionals have generally been willing to admit.

What is to be done?

If you can't beat 'em, join 'em. Scientists, engineers, and programmers have been contributing sophisticated entries to Wikipedia almost from the beginning. Two disciplines in particular—mathematics and music—have systematically sought to colonize Wikipedia on behalf of their scholarly communities. That's undoubtedly why Wikipedia's entry on Fermat's Last Theorem is so much better than Britannica's, and why the Wikipedia entry for so many composers and other musical subjects is often so good.

Because the discipline of history is much harder to corral than these more technical subjects, and because it's nearly impossible to imagine organizing historians to provide editorial input for all relevant Wikipedia pages, it would undoubtedly be more productive to approach this challenge in a "wikier" way. There are few pages on Wikipedia that couldn't be enhanced with more historical content. There are few historical entries that wouldn't benefit from more scholarly input. And there are myiad historical entries that are missing altogether. Given the openness of Wikipedia's protocols, improvements like these can be made by historians no matter what their training or institutional setting. Indeed, some teachers now require students to draft or revise Wikipedia entries as class assignments.

All one needs is to open oneself to the possibilities and give up the comfort of credentialed expertise to contribute to the greatest encyclopedia the world has ever known—which again, I intend here mainly as a symbol for the Web itself.

We might start with the entry for the American Historical Association. It's pretty inadequate, and would surely benefit from some scholarly revision.

Any volunteers?

William Cronon (Univ. of Wisconsin–Madison) is the president of the AHA.