In 1085, Moorish Toledo was conquered by Alfonso VI.

According to prof. Robert Sapolsky (he is a primatologist and neurobiologist, but usually all information he gives is very reliable), at the time of the conquest there was more cumulative information in the library of Toledo than in the whole Christendom, especially when it comes to philosophy and science. Could this be correct? How did repositories of knowledge (libraries) in Christian Europe compared with the Toledo library in number of volumes, reputation of authors, breadth and depth of topics covered, or other measures? In particular, how about the Byzantine libraries following the Carolingian Renaissance?

The answer has to contain some objective measure to fit the format of this forum, it could be e.g. the number of prominent antique/Arab philosophers whose works were known in Christian Europe before the conquest vs the books in the library, or some very significant works that were available in the library but not known in Christian Europe at the time, or any other objective measure that is available.

This is indirectly confirmed by the existence of Toledo School of Translators, but I could not find any quantitative references.

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    Most likely, even if enough people could agree on what measure to use, there would be no way to measure it.
    – Spencer
    Commented May 9, 2020 at 18:07
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    Imo, this is far too general a statement and it would be at Mr Sapolsky to provide evidence for his assessment, not at us to value or discard it. Frequently, such generalized statements turn out to be without a factual base. Europe was quite diverse during the medieval, because of different languages and dialects, societies, cultural units, .... But I am not an expert in these times.
    – user43870
    Commented May 9, 2020 at 19:06
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    @YuliaV: how about "Carolingian Rennaissance", Byzantine, don't they count for Christianity ? Didn't they include traded knowledge from the Antique as well ? Not that i want to defend them, just throwing in that things might have different measurements here ...
    – user43870
    Commented May 9, 2020 at 19:12
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    Regarding libraries in Byzantine empire, the best answer, I think, is that "we do not know," and am I sure, Dr. Sapolsky does not know either. One can only conjecture that much of the imperial library was destroyed in 1204 (the 4th Crusade). Personally, I prefer to treat claims like the one made by Sapolsky with Hitchens's razor. Commented May 9, 2020 at 22:07
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    I have (hopefully) clarified the question and nominate it for reopening in its current form.
    – Tom Au
    Commented May 10, 2020 at 7:59

2 Answers 2


The volume of information in the libraries of Andalusian Spain (Toledo, Cordoba and Granada) truly dwarfed what was available in most of Christendom at the time. Andalusian libraries and their affiliated network of local suppliers:

churned out as many as 60,000 treatises, poems, polemics and compilations a year. [...] This level of industry was in sharp contrast to the knowledge production underway throughout much of Christendom, where during the same period the two largest libraries (Avignon and Sorbonne) contained at most 2000 volumes as late as 1150. (source, available on sci-hub)

If we take Sapolsky to mean Western Christendom, his comparison is clearly accurate. However, as mentioned in the comments, it is feasible that the libraries of Byzantium may have rivaled those of Moorish Andalusia. I'm not seeing good numbers with which to make that comparison.

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    I'm reminded of the discovery of Roman and Greek scrolls in Pompeii which, it was hoped, would greatly widen our knowledge of ancient literature. Except that it turned out to be all about the writings of a Greek philosopher who was more-or-less the Greek Rod McKuen. I.e., quantity isn't meaningful without understanding what it's 60,000 scrolls of. (Even if your source (which I can't open) is valid.)
    – Mark Olson
    Commented Apr 14, 2021 at 21:41
  • Updated source links
    – Brian Z
    Commented Apr 14, 2021 at 21:47

It is almost impossible to know exactly how many textual works were compiled within Medieval Libraries; one can only offer speculations and theories, due to the lack of primary historical evidence.

We know that Libraries did exist in Medieval Spain, both in Toledo, as well as Cordoba. Constantinople had its own imperial Library which stood for centuries, though it was destroyed by The Crusaders in 1204.

The Sorbonne/University of Paris had its own Library though its collections, when compared with the Library of Toledo, as well as the imperial Library of Constantinople, were probably much smaller-(it should be noted that Thomas Aquinas, taught at The University of Paris). Keep in mind that Paris, 800-900 years ago, was not the Paris of today. The economic wealth, political power and overall cultural sophistication of Medieval Paris, was a far cry from the economic wealth, political power and overall cultural sophistication of Modern and contemporary Paris. During the Middle Ages-(even during Aquinas' time, circa the 1200's), The Sorbonne/University of Paris would not have had the large financial resources, political power or sizable supply of Academics, Scholars, Librarians and Translators when compared with their Byzantine and especially, their Iberian counterparts. Cities, such as Constantinople, Cordoba (and perhaps Toledo), were, arguably, the Paris of the Middle Ages.

  • The sack of 1204 doubtless destroyed much, but (1) A manuscript that exists in only one copy is pretty much doomed, anyway. Papyrus in particular needed to be recopied regularly to reliably survive. (2) When the Ottoman conquest finally ended the Byzantine Empire many scholars fled West (and helped fuel the Renaissance). They couldn't have existed without a lot of written materials. (It would be interesting to learn how much came West with them.) Finally, (3) I find it very unlikely that Constantinople had the only manuscript collection in the East.
    – Mark Olson
    Commented Apr 14, 2021 at 21:49
  • You make some good points and yes I tend to agree with you regarding manuscript collection and the Medieval East. While Constantinople probably dominated or accumulated many more manuscripts than their Eastern counterparts, yes, other cities of the East, such as Cairo, Baghdad (as well as perhaps Antioch in Northern Syria) and possibly the cities of Uzbekistan-(the land where Algebra was created 1200 years ago), probably had their own impressive collection of manuscripts.
    – user49540
    Commented Apr 14, 2021 at 21:54

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