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Wikipedia is many things, more concretely: many encyclopedias to many people, and that is one of its greatest strengths: it is a general encyclopedia, but it is also many specialist encyclopedias. Any conflicts arising through Wikipedia's multi-faceted nature should be resolved in such a way that Wikipedia remains a useful resource for all the different segments of its readership. In some cases, this might result in the need for, yes, two different articles treating the same subject on two different levels; the resulting "Introduction to..." articles should not be shunned as un-encyclopedic, they should be accepted for what they are: a necessary tool that allows Wikipedia to remain many things for many people. Live and let live – and make Wikipedia as useful as possible for as many readers as possible.

Wikipedia's readership is quite varied, and that is a good thing. Readers will look for many different articles they could not expect to find in your generalist, run–of–the–paper-mill encyclopedia, and indeed they are bound to find them, since there are sure to be editors sharing the same interests. Compared with all dead-tree encyclopedias like the Britannica, we have an inordinate number of articles about TV series, pop bands and other musical groups. Taking pars pro toto the example of a pop group whose every song appears to have an article (making for a total of roughly 300 articles about this group alone), we might call this Wikipedia's inordinate fondness for Beatles. If we had any space limitations, such as any printed encyclopedia has, there would be heated discussions about the appropriateness of such articles – should we stick to classic encyclopedia content? or, since the prototypical "curious average reader" is nowadays more interested in "Hey Jude", to take one pick from Wikipedia:Featured articles, than in Prehistoric Georgia, should we drop the latter to accommodate the former?

Luckily, we have no such space limitations. The different parts of the readership can coexist peacefully side by side; except for encyclopedia purists, no one is going to be bothered if there are articles in Wikipedia you wouldn't find outside specialist encyclopedias in the regular book world. We should be proud that Wikipedia is so many things to so many people – a regular encyclopedia to those who want to save the space that used to be taken up by their Britannica, and a host of specialist encyclopedias to a variety of readers with more specialized interests.

Sometimes, being many things to many people can lead to complications. For whom are we writing this? Are we writing for the college student? The "man in the street"? The "average curious reader", whoever they may be?

Again, since we do not have significant space limitations, this is less of a problem than it might be. Frequently, specialization will simply take the form of many detailed spin-off articles. If you are greatly interested in the Roman Army, then the level of detail you are bound to aim for as an editor will lead to the creation of many more specialized articles ("spinout"), in this particular case Structural history of the Roman military, Campaign history of the Roman military, Technological history of the Roman military, and Political history of the Roman military. For these articles, the target audience will certainly not be the "curious average reader" any more, whose interest in the Roman army, let's face it, is unlikely to run as deep as all that. But that is OK – for the average reader, there will be the base article Roman Army; for the interested student or those with special interests who want to dig deeper, there will be the more detailed articles.

Once more, no-one would ever demand to remove the more detailed articles on the ground that for all but a few readers, interest in the subject just doesn't run that deep – there is no conflict between the different audiences; the fact that there is material at the level of college textbooks does not harm the less specialized reader. The result is that, in subject areas like this, Wikipedia is a valuable resource both for college students and for someone who's just seen a History Channel program about the Roman army and now wants to know just a little bit (but not too much) more. Which is, again, a good thing, and something to be proud of.

Oh, and the fact that we're not short of space (do I hear servers creaking?) also takes care of one other conflict between writing for a general and for a special audience. If you've ever had to haggle with an editor about how many footnotes and references to include in, say, a popular science book (if we include more pages, the book will become more expensive! hardly anyone will read the footnotes anyway!), you'll appreciate this properly. Wikipedia articles can, and in fact should, cite their sources – another feature that makes them eminently useful even for more specialized readers.

Onwards and more-specialized-wards: if you're an average curious reader perusing, say, the Political history of the Roman military, you might find it a bit too detailed for your taste, but, the occasional Latin word and a possible lack of appreciation for subtleties notwithstanding, you will in general understand what you're reading there. Not so with an article like, say, automorphic form. For a certain subset of the Wikipedia audience, namely those who study college-level mathematics or physics, this is an eminently useful article. It is certainly not accessible to a general audience. Should it be deleted?

So far it hasn't been, and a good thing, too. We have no space problem. The fact that this article is on Wikipedia doesn't take anything away from the "curious average reader" (who will, in all but a very few cases, not even notice its existence), and it does give something to mathematically inclined Wikipedia users. Live and let live. In fact, many of those who study mathematics and/or physics at college level or beyond (many researchers, come to that) regularly use Wikipedia when it comes to quickly looking up formulae or mathematical definitions. By including such articles, we can certainly no longer argue that all articles on Wikipedia must be in toto accessible to a general audience. But again, Wikipedia is many things to many people, and it would seem both narrow-minded and pointless to restrict its usefulness to one part of the readership if no-one profits from that restriction.

Not to create the mistaken impression that this stance is of groundbreaking originality, I hasten to add that it is actually reflected in the guidelines, namely in Wikipedia:Make technical articles accessible. Under the heading Technical content, it says that articles on very technical subjects belong in the encyclopedia; however, the technical part should at least be preceded by a more generally accessible introduction. Sadly, that does not seem to be the case for most mathematics articles yet, which is something to work on (although, admittedly, the chances of the curious average reader stumbling upon an article like Splitting field are not all that high). But let us note that here is another example of peaceful coexistence, of Wikipedia successfully being different things to different portions of its readership: Even an article that, to be useful to the specialist, needs to be written in a way that makes it inaccessible to the general readership (for instance by freely using the language of mathematics), can be a helpful resource to the curious average reader as long as the technical part is preceded by an accessible lead.

While the examples here are from mathematics and the sciences, this is a mere artifact of the essayist's own specialization. Surely the same will apply to specialized articles in, say, Literary theory as well.

What of cases in which the resolution strategies mentioned so far – specialized sub-articles, accessible lead plus technical main text – do not work? To be sure, such cases are likely to be rare; an article like that would need to have the following properties:

• The "curious average man" is interested enough in the subject to want to know more than what is contained in the lead
• The subject matter is complex enough (involving unfamiliar concepts such as those of advanced mathematics) that a four-paragraph lead simply does not allow sufficient space for adequate explanations
• For the article to be useful to those with a more specialized interest, it must contain a considerable amount of information that is unavoidably technical; taking away that information significantly reduces usefulness

For example, take general relativity (and, in fact, a first version of this essay formed part of the Featured article candidate discussion for Introduction to general relativity). It is certainly of general interest (as the large number of popular science books on the subject vividly attests). It is certainly not possible to sum it up in an accessible way in a mere four paragraphs – not if the reader is meant to get at least an overview of what the theory is about. And it certainly has a specialist readership, as well – the same readership as the relevant entry in the Encyclopedia of Science and Technology, to give an example.

What to do?

Leave out the technical stuff altogether? That would certainly be a step towards accessibility, but would severely diminish the use of the article for more specialized readers. One major factor of what makes Wikipedia come alive are its internal links. Wikipedia is a semantic web, and for a specialist, an article such as general relativity will be a central hub, linking technical terms like differentiable manifold or tensor or differential equation to one of their most important applications. Leave those technical terms out, and you have torn up that web. Someone who's heard about tensors, and happens to be reading this article, is denied the crucial information that the one plays an important role in the other. If this were a strict trade-off, I would be all for making the article accessible to a general audience. Let's hold onto this for a moment.

Include the technical terms in parentheses only? Sometimes, that works. For instance, I would argue that the Structural history of the Roman military does not become markedly more inaccessible by including unavoidably technical terms like "hastati" or "socii". Sure, some readers might feel a bit overwhelmed, but all in all, it's a good compromise – the terms are there for those with a more specialized interest, and they do not harm those more superficially interested. But this will work only when there is the possibility of finding concise alternative formulations. If I talk about "a sword known as a gladius", that's certainly accessible. Everyone has a mental image of what a sword is, and one which is close enough to the more specialized usage to be useful. But what about, say, differential equations? Talking about "equations that involve not only functions, that is, descriptions of how one quantity varies depending on another quantity, but also rates of change of such functions, known as differential equations" is a mouthful, and not accessible at all. Sure, I can explain in more detail, which already makes the text more tedious to read for specialists. But even that isn't ideal. There is an analogy from linguistics: A word-for-word translation of a text written in a foreign language is, in one sense, closer to the original, but it is not in general a good text. Similarly, a series of term-by-term explanations of mathematical terms usually makes for a much, much less accessible explanation of the underlying physics than an explanation that does not slavishly stick to the technical terms, but instead makes an effort to convey the essence of the underlying physics. If I choose the latter variety, of course, I will need to leave out most technical terms altogether, so I'm making the text much less valuable to the more specialized reader. Sometimes, there just isn't a good compromise.

Alternate non-technical and technical explanations? Can you write the article by developing the subject once (touching all the necessary bases), but at each step, first give an accessible account, and then follow up with the technicalities? I fail to see how, in the cases under discussion here, that can ever make for an excellent article. A reader without previous knowledge will, in each section or even in every other paragraph, be confronted with technical content they don't understand. Even if you tell that reader that, by just reading, say, the first paragraph of each subsection, they should get a good overview, this kind of reading is frustrating; if you do not explicitly tell the reader how to read, most are going to decide even after the first paragraph that this is much too technical for them to understand. For the most specialized readers, this is also sub-optimal. In browsing the text, they will encounter each explanation twice, which will certainly interrupt reading flow (not as bad as only understanding half of what is written, but still). Such an article will be mediocre for both groups, but excellent for none.

Non-technical first, technical later? This is much less frustrating for all involved: Add an introduction first, the technical stuff after that. General readers will read the introduction and be happy; the same step-by-step development of the subject will be repeated at a higher level afterwards for the more technically inclined, which will also be happy. Nothing against that – it's the logical continuation of the way it is (or should be) done for other unavoidably technical articles: General description in the lead, gory details after that. However, once we're there, there will be the length issue. An accessible explanation is quite a feat, and, paraphrasing Rudy Clark, it's gonna take space. But that's OK, after all, we've had this problem with other subsections before; now that we have it with the lead, there's the analogous solution: Make the subsection into its own article. Such a spinout of the lead of article X is commonly called an "Introduction to X"; for our example, general relativity, there exists a companion Introduction to general relativity. The guideline Wikipedia:Make technical articles accessible, in which the creation of such introductions is encouraged wherever appropriate, also calls them "trampoline articles", since they might serve as an aid for readers who will read the introduction first and, thus fortified, move on to the main article. A list of current "Introduction to" articles can be found here.

While there have been vociferous objections to the very existence of such articles (one particular variety of exclusionism), they are a natural application of the spinout principle. Most importantly, they are a key tool when it comes to ensuring that Wikipedia is many things to many people, resolving, as they do, the conflict between the different requirements that the "average curious reader" and the more specialized reader might have for an article on one and the same topic.

The multi-faceted nature of Wikipedia is part of what makes Wikipedia special. Whenever possible, live and let live – do not make Wikipedia inaccessible for one of its many types of readers if you can avoid it, and do not assume that all readers of Wikipedia share your particular degree of interest or disinterest, specialization or general outlook concerning a given subject. Still, this principle should never be used as an excuse for writing bad articles or for not following Wikipedia:Make technical articles accessible. In particular:

• Even if you are writing an article that is very likely too detailed to be of interest to the curious average reader, do not fall into specialist jargon. If you can, keep the article accessible.
• Even if you are writing a highly technical article mainly aimed at specialists, please add an accessible lead.
• The existence of an "Introduction to" page should never be used as an excuse not to make the main article more accessible.
• Conversely, think long and hard before starting an "Introduction to". Is it really necessary? Or could the main article be changed so as to remain useful for the specialist, yet become accessible to more general readers?
• Accessibility does not have to mean dumbing down. If you are a specialist writing an "Introduction to", do not talk down to your readers. Many of them will be quite as intelligent as you are. Thinking out good simplifications that are both accessible and yet do justice to your subject is hard work, but it's worth it.

Finally, Wikipedia is certainly not all things to all people. Make Wikipedia the most versatile encyclopedia it can be, but do not try to make it what it is not (a dictionary, a text-book, a soapbox).