Deletionism is a term used to describe Wikipedians that favor clear and relatively rigorous standards for accepting articles, templates or other pages to the encyclopedia. Conversely, Wikipedians who believe that there ought to be few or no standards barring an article from Wikipedia are said to subscribe to inclusionism. Few editors would explicitly describe themselves as "deletionists", rather the term is often applied as a slur, as self-deprecating humor, or simply used to expose contrast with people describing themselves as inclusionists.
Wikipedians who subscribe to a conservative inclusion philosophy are likely to request removal of an article they believe does not meet standards. Many editors' inclusion philosophies are dependent on the subject area. For example, some people have more expansive views about removing or deleting unsourced/poorly-sourced biographies of living people from the Wikipedia project, because of the increased risk of harm these articles can represent.
The narrower viewpoint on inclusion does not usually insist that useful information should be deleted. Rather, the decision to keep or eliminate an article is viewed by many as tool for organizing the information that the project retains. Most often, people promoting the deletion of an article support moving the most important information from that article into a larger parent article on the subject and leaving a redirect to the relevant section.
On most articles in Wikipedia, there is little disagreement between editors of either persuasion. Most Wikipedians would agree that articles such as Dwight D. Eisenhower and Evolution have a clear place in the encyclopedia, just as many Wikipedians want extremely poor content to be excluded from Wikipedia. Disagreements usually arise, however, with relatively poorly written articles, or articles on subjects of little note, especially those whose subjects are fictional in nature (such as characters from a work of fiction).
For example, some editors may hold that a short, poorly sourced article on an elementary school in an obscure location does not merit a page of its own in the encyclopedia. They may cite concerns about adequate references and verification of claims made in the article. They are more likely to suggest that it is unnecessary to create individual articles on topics that are difficult or impossible to reliably expand in adherence to the verifiability and citation policies of the encyclopedia. Inclusionists often suggest that such articles be kept regardless as they may form a nidus of editing later on; in this sense, inclusionism shares attributes of eventualism, whereas deletionism has similarities with immediatism and exclusionism.
Some argue that labeling positions as "deletionism" and "inclusionism" only leads to factionalism, which makes it difficult to foster cooperation and endangers the understanding of mutual positions. Instead of doing so, Wikipedians should try to develop meaningful policies in consensus which can be applied to resolve questionable cases. This can be done by building on existing policy, that is, by examining previous cases of deletions. Others argue that tensions can be reduced by recognizing this difference of tendency rather than denying it to create a false harmony, and instead setting policy and designing the software so that it allows the two tendencies to work with less conflict. And then there are those who consider it irrelevant whether there is an atmosphere of conflict or of co-operation, of tension or of harmony. They point out that Wikipedia is not a social club (although this idea may not have yet reached the Wiktionarians), and that the only important things here are the articles and the mechanisms that make their writing possible.
It is sometime proposed that technological de-escalation such as output filtering could resolve the conflict completely, but deletion itself is simply output filtering: The mediawiki software never actually deletes anything. "Deletion" merely hides the content from public view. Proposals to add additional levels of deletion, e.g. logged in users only for content which is below the threshold which can be well maintained and referenced, have not gained any traction.
It is inaccurate to label Wikipedians simply deletionists or inclusionists: There is a range of views, and many Wikipedians judge articles on their individual merits, forming conclusions that may be ascribed to different "philosophies" by others. An individual's standards for keeping or dropping an article may require a two or three dimensional representation to be accurately described, instead of a one-dimensional continuum. For example, a Wikipedian may be quite happy to keep stubs, provided that they are on-topic, but desire to delete (or move) large but off-topic articles.
An essay written on English Wikipedia long ago and subsequently deleted by its author, but which eloquently reflects the tension here, states:
 Rationale for deletion
- Some articles complicate indexing. For example, having articles on the many unnoteworthy individuals named John Anderson makes it difficult for readers to find the article about the notable U.S. presidential candidate with that name.
- Similarly, the presence of obscure subjects in lists and timelines makes it more difficult for readers to find key people and events.
- Some articles cover topics too obscure for the wiki process to work. For example, a topic where only a few dozen people have firsthand knowledge (or any knowledge at all) is unlikely to see expansion or error correction by anyone but the original author. If these articles are retained Wikipedia may gather larger amounts of incorrect information. It is arguably better to find no result in Wikipedia or an obviously incomplete result than outright incorrect information.
- Some believe that the presence of uninformative articles damage the project's usefulness and credibility, particularly when casual visitors encounter them through Internet search engines or Wikipedia's "random page" or "recent changes."
- Some argue that allowing small, uninformative articles to remain promotes poorly-written "drive-by" articles, and that by deleting them writers will be more likely to make informative, well-written articles, a kind of broken windows theory.
- Articles on obscure topics, even if they are in principle verifiable, tend to be very difficult to verify. Usually, the more obscure, the harder to verify. Actually verifying such articles, or sorting out verifiable facts from exaggeration and fiction, takes a great deal of time. Not verifying them opens the door to fiction and advertising. This also leads to a de facto collapse of the "no original research policy", which is one of the fundamental Wikipedia policies. Empirically, there have been a number of hoax articles which were difficult to prove to be hoaxes but which could have been easily been deleted by a sufficiently strict notability policy.
- For many subjects related to fictional characters or works, it's very difficult to ensure that an article would portray the subject from a real-world perspective. The most high-profile example of this was that at one time Wikipedia had an article for every single individual Pokemon, even though most of them exist as little more than minor actors in video games: that's because it is easy to write whole articles from the perspective of a video game guide, or from an in-universe perspective which treats plot elements of a TV show as real. Because of this, some Wikipedians argue that the content itself simply isn't appropriate for an encyclopedia, whereas an external wiki which had different rules on how to present content from a fictional universe would be ideal.
- Less notable articles (minor concepts, South Park episodes, etc.) are more likely to result in articles that are original research.
- Less notable articles may distract attention from improving important topics (big things in history for example) because energy is devoted to maintaining popular but fairly insignificant fandom.
- Because Wikipedia is not paper it can utilize things like section redirects and search to cover even the most obscure subjects without giving each its own free-standing article.
 Arguments against deletion
- Deletionism goes against the premise of Wikipedia: "Imagine a world in which every single person on the planet is given free access to the sum of all human knowledge. That's what we're doing." — Jimmy Wales, founder of Wikipedia.
- It's easy to criticize and delete, whereas it's much more difficult to do research and create content. "Better to light a candle than curse the darkness." — Peter Benenson, founder of Amnesty International.
- Article additions and expansions, and allowing time for them to occur, is highly superior to simply deleting articles.
- Instead of deleting articles altogether, they can be merged with other articles (see Mergism).
- Notability of articles is sometimes very subjective. For some, the US presidential candidate John Anderson might be a noted person; others who don't live in the United States might feel that the Scottish scientist John Anderson is more prominent.
- It can be discouraging when articles created by first-time contributors and newer users are deleted without (in their opinion) a good reason. In their view, at least, the subject matter is noteworthy.
- It can be frustrating for a reader to come to Wikipedia for information and inside find that the relevant article existed at one point but has been deleted. This discourages both Wikipedia readership and authorship.
- Deleting an article under the generic basis of notability both reduces Wikipedia to the level of traditional encyclopedias (which won't cover topics that Wikipedia will for various reasons, including notability), and also doesn't provide the oversight that a traditional encyclopedia has to justify it trimming articles. Part of the reason people use Wikipedia is that it is a vibrant source of obscure knowledge, especially about obscure topics that aren't covered in a more traditional encyclopedia. Other methods of ensuring quality, such as labeling a page "In Need of Editing and Sources", are more than enough to correct problems.
- The Wikipedia search engine was updated and improved in 2010, in which "Search suggestions are now improved to get you to the page you are looking for more quickly," as reported on the Wikimedia blog on May 13, 2010. (link: "A new look for Wikipedia". This serves to nullify the deletionist argument that "too many unnoteworthy or obscure articles impede finding the relevant stuff..." in Wikipedia searches.
- Search, categorization, and other technical measures for organization can diminish the difficulty in finding information even when there are many articles about insignificant subjects.
- Deletionists may subjectively pick-and-choose from a long and diverse list of Wikipedia notability and other guidelines as a rationale for the blanket deletion of an article. When one chosen standard is disproven, another rule is searched for and then stated as a rationale for deletion.
- Deletionists may use absolutist rationales and stances to justify article deletion. A notable example in Articles for deletion logs is arguing that absolutely no reliable sources exist to establish notability for and/or verify an article, while utilizing only one brief search for news and other sources, such as on Google or Google news, to qualify the statement. Sometimes it takes only seconds to disqualify such statements by utilizing web searches in other mediums, particularly those that are empirical, research-based, and lack a profit motive.
 See also
- Transwiki:Constructionism and reductionism (wiki)
- Association of Deletionist Wikipedians
- Association of Exclusionist Wikipedians
- Association of Inclusionist Wikipedians
- Association of Mergist Wikipedians
- Association of Wikipedians Who Dislike Making Broad Judgements About the Worthiness of a General Category of Article, and Who Are In Favor of the Deletion of Some Particularly Bad Articles, but That Doesn't Mean They are Deletionist
- Proposed policy for wiki closure
- Wikimedia fundraiser highlights webcomic community's frustration with Wikipedia guidelines