Many people say it, but few explain why. Many even say it without knowing why. So today, I’ll try to explain why Wikipedia is a bad source for your arguments.
Have you ever looked at the reference list on an article on Wikipedia? Not just seen it, but really looked at it? I often do, and there are things going on there that shouldn’t. A lot of references are blogs or microsites (one-page sites) with no source references themselves. This means that all someone needs to do to rewrite an article on Wikipedia is to first create a blog and write the same text there first. In fact, there’s nothing stopping me from going in after I’m done with this text, to use this on Wikipedia’s article about Wikipedia.
On a high-profile article such as that one, it’s harder to get away with it, as someone else will most probably flag it and it will get reviewed and removed quickly. Or will it? At the moment of writing, that very article has over 340 reference sources, one of which is simply the paragraph of text rewritten, without any links. 10 of the “sources” simply link back to Wikipedia again, with their “source” being listed as the article on Wikipedia, thus creating a closed loop. 3 sources are blogs, with no source reference in their articles. 5 links lead to a 404 page (meaning the page is now gone). That’s more than 5% of the sources unverifiable, on the article about Wikipedia itself.
There’s often several articles about the same subject, with different enough content to make it its own issue. These could and should have different sources, but sometimes these become a tad ridiculous. For example, an article about the safety of Uranium mining sourced a now defunct page on the Greenpeace website and had no other sources. Meanwhile, the page on the safety of using this Uranium in a nuclear reactor was referencing World Nuclear, a lobby organization for nuclear power.
Neither of these pages list sources for anything they say, and the pages are basically just fancy looking blogs.
Source the sources
Wikipedia is a great site, with a lot of collected information, but it shouldn’t be seen as a source of this information. With the articles being ever changing and the references changing just as often, it is put to a lot better use in other ways.
Start your research on Wikipedia. When you find the part of the article you’re interested in, check the source of it. If the source is anything but an opinion piece without their own sources, that is a good place to source from.
To reference Wikipedia as your source is like referencing the source of the text you’ve quoted. To blindly quote Wikipedia without checking the source is like letting someone else write the argument for you, without you knowing their intentions. There is currently no method for Wikipedia to ensure that the source is truthful, as it is written by its users. There is nothing that ensures the source is still there and nothing other than the keen eye of the users to rewrite the article, should a source disappear.
In an argument, you can quote a Wiki article, as long as you make sure your opponent knows you’ve ensured the source is valid. But then it’s just easier to quote the source directly.