Wikipedia:Verifiability

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The threshold for inclusion in Wikipedia is verifiability, not truth. "Verifiable" in this context means that any reader must be able to check that material added to Wikipedia has already been published by a reliable source, because Wikipedia does not publish original thought or original research.

Wikipedia:Verifiability is one of Wikipedia's three content-guiding policies. The other two are Wikipedia:No original research and Wikipedia:Neutral point of view. Jointly, these policies determine the type and quality of material that is acceptable in the main namespace. They should not be interpreted in isolation from one another, and editors should therefore try to familiarize themselves with all three. The principles upon which these three policies are based are only negotiable at the foundation level in practice.

The policy

1. Articles should contain only material that has been published by reputable sources. 2. Editors adding new material to an article should cite a reputable source, or it may be removed by any editor. 3. The obligation to provide a reputable source lies with the editors wishing to include the material, not on those seeking to remove it.

Verifiability, not truth

Template:Associations/Wikipedia Bad Things One of the keys to writing good encyclopedia articles is to understand that they must refer only to facts, assertions, theories, ideas, claims, opinions, and arguments that have already been published by reputable publishers. The goal of Wikipedia is to become a complete and reliable encyclopedia. Editors should cite reliable sources so that their edits may be verified by readers and other editors.

"Verifiability" in this context does not mean that editors are expected to verify whether, for example, the contents of a New York Times article are true. In fact, editors are strongly discouraged from conducting this kind of research, because original research may not be published in Wikipedia. Articles should contain only material that has been published by reliable sources, regardless of whether individual editors view that material as true or false. The threshold for inclusion in Wikipedia is thus verifiability, not truth.

A good way to look at the distinction between verifiability and truth is with the following example. Suppose you are writing a Wikipedia entry on a famous physicist's Theory X, which has been published in peer-reviewed journals and is therefore an appropriate subject for a Wikipedia article. However, in the course of writing the article, you contact the physicist and he tells you: "Actually, I now believe Theory X to be completely false." Even though you have this from the author himself, you cannot include the fact that he said it in your Wikipedia entry.

Why not? Because it is not verifiable in a way that would satisfy the Wikipedia readership or other editors. The readers don't know who you are. You can't include your telephone number so that every reader in the world can call you for confirmation. And even if they could, why should they believe you?

For the information to be acceptable to Wikipedia you would have to persuade a reputable news organization to publish your story first, which would then go through a process similar to peer review. It would be checked by a reporter, an editor, perhaps by a fact-checker, and if the story were problematic, it might be checked further by the lawyers and the editor-in-chief. These checks and balances exist to ensure that accurate and fair stories appear in the newspaper.

It is this fact-checking process that Wikipedia is not in a position to provide, which is why the no original research and verifiability policies are so important.

If the newspaper published the story, you could then include the information in your Wikipedia entry, citing the newspaper article as your source.

Sources

Further information: Wikipedia:Reliable sources

Articles should rely on credible, third-party sources with a reputation for fact-checking and accuracy. For academic subjects, the sources should preferably be peer-reviewed. Sources should also be appropriate to the claims made: outlandish claims beg strong sources.

English-language sources should be given whenever possible, and should always be used in preference to foreign-language sources, so that readers can easily verify that the source material has been used correctly.

Burden of evidence

For how to write citations, see Wikipedia:Citing sources

The burden of evidence lies with the editors who have made an edit or wish an edit to remain. Editors should therefore provide references. If an article topic has no reputable, reliable, third-party sources, Wikipedia should not have an article on that topic.

Any edit lacking a source may be removed, but some editors may object if you remove material without giving people a chance to provide references. If you want to request a source for an unsourced statement, a good idea is to move it to the talk page. Alternatively, you may tag the sentence by adding the {{fact}} template, or tag the article by adding {{not verified}} or {{unsourced}}. Also in that case it may be helpful for your co-editors to leave a clarifying note on the talk page, for instance indicating which sources you already checked. You can also make the unsourced sentences invisible in the article by adding <!-- before the section you want to comment out and --> after it, until reliable sources have been provided. When using this "commenting out" technique it is usually best to leave a clarifying note on the talk page.

Be careful not to err too far on the side of not upsetting other editors by leaving unsourced information in articles for too long, or at all in the case of information about living people. Jimmy Wales has said of this: "I can NOT emphasize this enough. There seems to be a terrible bias among some editors that some sort of random speculative 'I heard it somewhere' pseudo information is to be tagged with a 'needs a cite' tag. Wrong. It should be removed, aggressively, unless it can be sourced. This is true of all information, but it is particularly true of negative information about living persons."

Burden of evidence in biographies of living persons

Biographies of living people need special care because biographies containing unsourced material might negatively affect someone's life and could have legal consequences. Remove unsourced material about living persons immediately if it could be viewed as criticism, and do not move it to the talk page. This also applies to material about living persons in other articles. See Wikipedia:Biographies of living persons and Wikipedia:Libel. When removing information be careful to observe Wikipedia:Civility.

Sources of dubious reliability

In general, sources of dubious reliability are sources with a poor reputation for fact-checking, or with no fact-checking facilities or editorial oversight.

Sometimes a statement can only be found in a publication of dubious reliability, such as a tabloid newspaper. If the statement is relatively unimportant, remove it. If it is important enough to keep, attribute it to the source in question. For example: "According to the British tabloid newspaper The Sun..."

As a rule of thumb, sources of dubious reliability should only be used in articles about themselves. (See below.)

A Wikipedia article about an unreliable newspaper should not — on the grounds of needing to give examples of their published stories — repeat any claims the newspaper has made about third parties, unless the stories have been published by other credible third-party sources.

Self-published sources (online and paper)

See also Wikipedia:Reliable sources#Using online and self-published sources

Anyone can create a website or pay to have a book published, and then claim to be an expert in a certain field. For that reason, self-published books, personal websites, and blogs are largely not acceptable as sources.

Exceptions may be when a well-known, professional researcher in a relevant field, or a well-known professional journalist has produced self-published material. In some cases, these may be acceptable as sources, so long as their work has been previously published by reliable third-party publications. However, exercise caution: if the information in question is really worth reporting, someone else is likely to have done so.

Self-published and dubious sources in articles about themselves

Material from self-published sources, and other published sources of dubious reliability, may be used as sources of information about themselves in articles about themselves, so long as:

• It is relevant to the person's or organization's notability;
• It is not contentious;
• It is not unduly self-serving;
• It does not involve claims about third parties, or about events not directly related to the subject;
• There is no reasonable doubt about who wrote it.

Other comments

Just because some information is verifiable, doesn't mean that Wikipedia is the right place to publish it. Verifiability is a necessary but not sufficient condition for an article. See what Wikipedia is not. Just because information is true, doesn't mean that it meets our verifiability requirements — information has to be sourced from reliable sources if it is to have a place in Wikipedia (although, of course, if information is true, you should be able to find a ready reputable source for it). Another effect of this policy is that as original research will not be supported by reputable sources, it cannot be included. See Wikipedia:No original research.

A thought: Tacitus' recommendation

nos consensum auctorum secuturi, quae diversa prodiderint sub nominibus ipsorum trademus.		Proposing as I do to follow the consentient testimony of historians, I shall give the differences in their narratives under the writers' names.
Tacitus, Annals XIII, 20 – Church/Brodribb translation

See also

• WikiProject Fact and Reference Check
• Forum for Encyclopedic Standards
• Stable versions
• Wikipedia:Biographies of living persons
• Wikipedia:Criticism

Further reading

• Jimmy Wales. "WikiEN-l insist on sources", WikiEN-l mailing list, July 19, 2006.