Our standard for inclusion of content on Wikipedia is verifiability, that is, whether a particular claim has been published by a reliable source. To emphasize this, the phrase "Verifiability, not truth" was created. This was designed to help settle arguments, especially with people who want to insert fringe beliefs or opinions as factual and are willing to edit war over it.
 | This page in a nutshell: "Verifiability in reliable sources is absolutely critical. But elevating that to a religion which rejects truth is a huge mistake." - Jimbo |
This essay's position is that truth on Wikipedia does matter, and that claiming that it doesn't is at best disingenuous, and at worst, counterproductive to nuanced content dispute conversations.
Our core policy of neutral point of view (NPOV) is primarily concerned with truth. A long-standing summary of NPOV was "Assert facts, including facts about opinions—but don't assert opinions themselves.".[1] A "fact" is something that is objectively true. So, NPOV directs us to state only objectively truthful things using Wikipedia's voice. Evaluations of the truth of a claim are central to following the policy of NPOV.
We generally have two ways of presenting claims without resorting to weasel phrasing. In Wikipedia's voice as a plain assertion of fact, or assigned as the position of a specific third party ("According to foo....").
Our articles would look ridiculous if, for example, the article Sun opened with "According to NASA scientists, the Sun is the star at the center of the solar system." At some point someone made an evaluation of the truth of that claim, and decided that it was factual enough to say it in Wikipedia's voice: "The Sun is the star at the center of the solar system."
Evaluation of truth is separate from our normal editing process where unsourced statements may be challenged and/or removed, and only restored with sourcing. If a flat earth believer removed the claim that the sun was the center of our solar system, and it was restored with sourcing, we generally would not change to the "asserting a fact about an opinion" wording, merely because that fact was disputed. On a practical and philosophical level, controversy alone does not transform a fact into an opinion. That said, controversy may in some cases be an indication that a supposed "fact" isn't factual.
Under many definitions of defamation, such as California's, truth absolutely matters.
That [name of defendant] failed to use reasonable care to determine the truth or falsity of the statement(s)[2]
This is still the main thrust of the policy, though now it's expressed in a bulleted list that says (combining two items): Avoid stating opinions as facts and avoid presenting uncontested factual assertions as mere opinion.
