Wikipedia:When sources are wrong

This is an essay. 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.

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Sources are wrong sometimes. They usually aren't; we try really hard to pick sources that will usually be right. But even those sources are sometimes wrong. Usually about little things, sometimes about big things, on rare occasions about critical things. Wikipedia:Neutral point of view gives us guidance for when sources disagree on matters of opinion, like if some sources characterize something as a language and some characterize it as a dialect. Wikipedia:No original research, and a litany of essays such as Wikipedia:The Truth, give us guidance for when we personally disagree with a source based on our own subjective views. But what about when sources disagree on basic facts, and one source is just clearly right, or where a source makes a claim that defies common sense and does not make a compelling case for its veracity? This essay outlines a few different approaches to such situations, based on actual examples, including ones encountered in writing good and featured articles.

Six approaches are given below, and can be synthesized as:

• If a source is trivially wrong, either ignore it (Approach 1), emphasize the correct answer without noting the error (2), or, if the error is particularly relevant, mention it in a footnote (3) or rarely prose (4a).
• If an error is significant but there is still a clearly right answer, mention it in a footnote (3), or in prose (4a) if it is of encyclopedic note.
• If there is a rough consensus of sources, state that in prose, while elaborating in a footnote (3) or prose (4b) based on the significance of the matter.
• If it is actually unclear what the correct answer is, but there is strong reason to think many or most sources are wrong or there is nothing approaching a consensus of sources, explain the conflict in prose (4b/4c) or do not discuss the topic at all (5).
• In rare cases, potentially include a likely incorrect statement (or even article) if there is no way to justify another approach as within editorial discretion (6).