This is related to my other recent question.

As I wrote there, it is hard to check book sources, especially if they are old and/or out-of-print. Occasionally, they can be found on Google Books, but this is a rarity.

I think that lots of us would trust a book more than the average website, but here it becomes hard to check that the book actually says what the poster claims it says. What are your thoughts on the matter? In some cases, are books preferable, or websites? Do we want answers that use websites as sources so they can be checked?

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    $\begingroup$ ... it is hard to check book sources, especially if they are old and/or out-of-print. Occasionally, they can be found on Google Books, but this is a rarity Curiously, I find the opposite. In fact, I found it quite easy to locate digitial copies for essentially EVERY reference in my recent question/answer, and it was only the more recent (after about 1920 or so) references that wound up being behind pay walls that I couldn't access. All the old stuff is freely available, at least where I'm at. $\endgroup$ – Dave L Renfro Nov 21 '14 at 20:34
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    $\begingroup$ @DaveLRenfro: this depends very much on your position and location. Some of us are affiliated with university libraries which make almost every book available (via ILL, for example). But for those who are not, Internet can be the only available resource. And HDE is right: very small portion of old books are available FREE on the Internet. $\endgroup$ – Alexandre Eremenko Nov 22 '14 at 14:05
  • $\begingroup$ @Alexandre Eremenko: I'm not affiliated with a university nor do I have access (without going to a university library and filling out permission forms) to Math. Reviews or on-line journals (except those freely available). And yet I've managed to find just about anything I want on the internet, at least regarding items of historical interest. It's the more recent material (books and articles), after about 1920, that is difficult to find freely available digital versions. For another example, see my older references in this document. $\endgroup$ – Dave L Renfro Nov 24 '14 at 14:49
  • $\begingroup$ @Dave L Rentro: A comment addressed to me should be under my answer, not under the question. You are right: sometimes an 18-th century book is easier to obtain than a book after 1920. But most existing books are published after 1920, I believe. $\endgroup$ – Alexandre Eremenko Nov 24 '14 at 21:34

I think accuracy and intellectual rigor should always be the primary concern when citing a source. Accessibility is nice, but it should not be a policy. Sure, not everyone can access various obscure texts, but then again, if you live in certain countries, you might not be able to access many websites either. Given the choice between an out-of-print academic history text (which may be practically inaccessible for some users) and a sleazy website which doesn't cite any reliable sources and just spreads famous apocryphal stories with no fact-checking, I think we'd all agree that the first is a reasonably good source even if you can't read it personally, and the second is no better than having no source at all.

On the other hand, a self-published book making clearly absurd claims is less reliable than a well-referenced biography on a university history of science department website, so books aren't universally more trustworthy; it's a question of the author's methodology and references. Primary sources are the best insofar as they aren't biased. Secondary sources citing primary sources are typically trustworthy if they have good methodology. Even tertiary sources and higher are sometimes going to be good enough for relatively uncontroversial claims, but if a source is making claims without citation or with very weak citation you should be skeptical whether it's a website or a book. The average book is probably better than the average website, but there's a great deal of variation for both.

That said, it's important that the answer on our site is complete without having to consult any external source (be it a link or a book). If a question is raised about the actual content of the source, it seems reasonable to ask the person citing it to include a direct quote. The poster is probably not the only person with access to the content. Many users here are likely to have academic positions, either in math/science or in history, and as such have access to a great deal of relatively rare books; it would be much worse for this site if we decided these were invalid sources (thereby locking away a great fraction of knowledge on this topic). It's pretty unlikely that someone will find a source that no one else has any access to at all. So at least someone here should be able to verify any seriously controversial citations, but hopefully we can trust each other enough to not just lie about the content of a source that this will only rarely become an issue.

Addendum: I don't think we should put too much concern into questions like "Is source A better than source B?" in general. If both are acceptable sources which make the same claim, include whichever one you personally prefer (or both if you like). If they say different things, and both are similarly credible, rather than trying to sort out the controversy and determine which is correct (which would be original research, not the purpose of this site), you're better off saying that it's a debated point, and that A says X, B says Y, C says Z, etc. So while I support using the best sources available for any given question, if it isn't immediately clear which source is better (i.e. more accurate), don't try to force yourself to decide.

  • $\begingroup$ I agree. However, a point of clarification, given the historical nature of the site. Most scientific 17th to 19th century books were self published (the author paid to have them published, as is often made clear by the author). A publisher (who organized the printing and/or distributed the book) is listed as publisher. The reliability depends on the content, not on self or not self published. $\endgroup$ – Gottfried William Nov 21 '14 at 21:48
  • $\begingroup$ Similarly, we have to careful, including citing university-published texts. It depends on the content, not on the publisher. For example, here's an example: Sombart, Werner 1937, A New Social Philosophy, Princeton university press. This is a book recommending nazi-ism, a caste system, and economic planning by divine revelation of God to the "leader" and his ranking assistants. A typical argument from the book: aircraft must be banned, except for military purposes, because noisy. He's not joking. The fact that Princeton published this doesn't make it better as a source for anything. ;) $\endgroup$ – Gottfried William Nov 21 '14 at 21:56

HDE rises an important question: if one has no access to a good university library, obtaining old out-of-print books is difficult. Many of them are digitalized but one needs to pay, or have a subscription to read them. Same applies to scientific journals. I believe that most universities in the US have JSTOR subscription, but for most people this and other similar resources are not available, or available at a price they cannot afford.

On my opinion, we have to keep this in mind when we write questions and answers. First, the writer has to evaluate herself the reliability of the source she cites, second, freely accessible sources should be preferred to those not freely accessible, and in many cases several sources can be given.

Let me give an example: the most important and comprehensive book on the ancient astronomy is Neugebauer's History of Ancient mathematical astronomy in 3 volumes. It was published in 1975, now out of print, and as far as I know it was never digitalized. Except a good university library you can find it only in the used books stores for \$300-$400. But this is really the most authoritative source on the ancient astronomy.

It is a shame, of course that the publisher (Springer) who apparently holds the copyright does not make it available. But what can we do about this? It is a very serious issue that scientific results, which should be available to everyone, have been "appropriated" by the publishers who consider them their private property, see for example, see for example http://en.wikipedia.org/wiki/The_Cost_of_Knowledge


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