 | This is an essay on the Verifiability policy. It contains the advice or opinions of one or more Wikipedia contributors. This page is not an encyclopedia article, nor is it one of Wikipedia's policies or guidelines, as it has not been thoroughly vetted by the community. Some essays represent widespread norms; others only represent minority viewpoints. |
 | This page in a nutshell: Any material added to Wikipedia must have been published previously by a reliable source. Editors may not add content solely because they believe it is true, nor delete content they believe to be untrue, unless they have verified beforehand with a reliable source. |
Wikipedia's core sourcing policy, Wikipedia:Verifiability, previously defined the threshold for inclusion in Wikipedia as "verifiability, not truth". "Verifiability" was used in this context to mean that material added to Wikipedia must have been published previously by a reliable source. Editors may not add information to articles simply because they believe it to be true, or even if they know it to be true.
The phrase "the threshold for inclusion is verifiability, not truth" meant that verifiability is a necessary condition (a minimum requirement) for the inclusion of material, though it is not a sufficient condition (it may not be enough). Sources must also be appropriate, used carefully, and balanced relative to other sources per Wikipedia's policy on due weight.
Wikipedia's articles should be intelligent summaries and reflections of current published knowledge within the relevant fields, an overview of the relevant literature. The Verifiability policy is related to another core content policy, Neutral point of view, which holds that we include all significant views on a subject. Citing reliable sources, for any material challenged or likely to be challenged, gives readers the chance to check for themselves that the most appropriate sources have been used, and used well (see below).
The phrase was removed from the verifiability policy in 2012 (but remains in a historical footnote). The revised wording clarified that "content is determined by previously published information rather than the beliefs or experiences of its editors. Even if you're sure something is true, it must be verifiable before you can add it". That we have rules for the inclusion of material does not mean Wikipedians have no respect for truth and accuracy, just as a court's reliance on rules of evidence does not mean the court does not respect truth. Wikipedia values accuracy, but it requires verifiability. Wikipedia does not try to impose "the truth" on its readers, and does not ask that they trust something just because they read it in Wikipedia. We empower our readers. We don't ask for their blind trust.
Sometimes we know for sure that the reliable sources are in error, but we cannot find replacement sources that are correct. As Douglas Adams wrote of The Hitchhiker's Guide to the Galaxy, "Where it is inaccurate it is at least definitively inaccurate. In cases of major discrepancy it's always reality that's got it wrong."