Photodisc

The idea of an encyclopedia—a compendium of all the best available knowledge—is as tempting as it is flawed. Truth does not always come in bite-sized chunks. And the notion of an infinitely elastic internet encyclopedia, always up to date and distilling the collective wisdom of the wired is even more tempting. When open to all comers, anonymously, the problems are even more glaring.

This week a senior Wikipedia editor, who used the pseudonym Essjay, turned out not to be a professor of religious studies as he claimed, but in fact a 24-year-old college drop-out. That has highlighted both the strengths and the failings of the world's biggest online encyclopedia, which now boasts well over 1.5m articles. The “Encyclopedia Britannica”, by contrast, has a mere 120,000.

Essjay (or Ryan Jordan in real life), got away with his pretence because Wikipedians jealously preserve their anonymity. With most entries, anyone can edit without even logging in; or they can create an entirely fictitious online identity before doing so. The effect is rather like an online role-playing game. Indeed, it is easy to imagine some sad fellow spending the morning pretending to be a polyglot professor on Wikipedia, and then becoming a buxom red-head on “Second Life”, a virtual online world, in the afternoon.

That anonymity creates a phoney equality, which puts cranks and experts on the same footing. The same egalitarian approach starts off by regarding all sources as equal, regardless of merit. If a peer-reviewed journal says one thing and a non-specialist newspaper report another, the Wikipedia entry is likely solemnly to cite them both, saying that the truth is disputed. If the cranky believe the latter and the experts the former, the result will be wearisome online editing wars before something approaching the academic mainstream consensus gains the weight it should.

Wikipedia has strengths too, chiefly the resilient power of collective common sense. It benefits from the volunteer efforts of many thousands of outside contributors and editors. If one drops out, another fills his place. People are vigilant on issues that interest them. When mistakes happen, they are usually resolved quickly. This correspondent's modest Wikipedia entry was edited this week by an anonymous contributor who posted a series of entertaining but defamatory remarks; a mere four minutes later, another user had removed them.

Constant scrutiny and editing means even the worst articles are gradually getting better, while the best ones are kept nicely polished and up to date. Someone, eventually, will spot even the tiniest error, or tighten a patch of sloppy prose. Mr Jordan, for all his bragging, seems to have been a scrupulous and effective editor.

The most tiresome contributors do get banned eventually, though they can always log in under a new identity. Other shortcomings are the subject of earnest internal debate too, such as Wikipedia's inherent bias towards trivial recent events rather than important historical ones. That is already changing, slowly, though subjects of interest to northern white computer-literate males are over-covered, while others are laughably neglected.

Wikipedia is the biggest collaborative online encyclopedia, but not the only one. Citizendium, supposedly launching soon, aims to be like Wikipedia but without anonymity, and with more weight given to recognised experts. Conservapedia aims to offer a version of the truth untainted by Wikipedia's liberal secular bias on issues such as evolution.

So how useful is Wikipedia? Entries on uncontentious issues—logarithms, for example—are often admirable. The quality of writing is often a good guide to an entry's usefulness: inelegant or ranting prose usually reflects muddled thoughts and incomplete information. A regular user soon gets a feel for what to trust.

Those on contentious issues are useful in a different way. The information may be only roughly balanced. But the furiously contested entries on, say, “Armenian genocide” or “Scientology”, and their attached discussion pages, do give the reader a useful idea about the contours of the arguments, and the conflicting sources and approaches. In short: it would be unwise to rely on Wikipedia as the final word, but it can be an excellent jumping off point.