Of course we'll never know for sure, but do historians have some reasonable ideas about what knowledge may have been lost at the Library of Serapeum of Alexandria, when it was destroyed by the Decree of Theodosius in 391?

From the movie "Agora" it is shown that the pagan occupants attempted to save whatever they could, and suggests that there may have been philosophical, mathematical, and astronomical research. However, Wikipedia information suggests that at this time the library may not have had such information:

The Serapeum housed part of the Great Library, but it is not known how many, if any, books were contained in it at the time of destruction. Notably, the passage by Socrates makes no clear reference to a library or its contents, only to religious objects. An earlier text by the historian Ammianus Marcellinus indicates that, whatever books might earlier have been housed at the Serapeum, none was there in the last decade of the 4th century. The pagan author Eunapius of Sardis witnessed the demolition, and though he detested Christians, and was a scholar, his account of the Serapeum's destruction makes no mention of any library.

So, my question is: in this or other destructive events, did the Library of Alexandria house information that was lost, and caused for lack of a better term, a setback for the progress of human knowledge?


Italian author Lucio Russo in his book "Forgotten revolution" argues that a large part of the scientific knowledge of Hellenistic world has been lost. I find his arguments very convincing.

Exact sciences in the modern sense of this word originated in Ptolemaic Egypt and other Hellenistic states, and reached very high degree of development. Few first class works survived, like Euclid, Apollonius and Archimedes, but there is a lot of evidence that this is just a tip of the iceberg. For example, almost all writings of Hipparchus, "the father of astronomy" are lost. We know about them from the account of C. Ptolemy who lived 3 centuries later. Or look at the "Antikythera mechanism" on Wikipedia and elsewhere, to get some evidence of what was lost.

L. Russo is a mathematician, and on his opinion, the level of development in some areas of mathematics in Hellenistic time was not really surpassed until XIX century. I am also a mathematician, and I confirm this.

This does not only apply to exact sciences. Critical scientific study of ancient texts, as we understand it now, also apparently originated in these Hellenistic states.

A legend says that one of the Ptolemy rulers tried to buy (from Athens) original texts of Aeschylus, Sophocles and Euripides. Athenians refused. Then he asked to borrow them to copy. Athenians agreed, but required an enormous security deposit. He payed the deposit, and did not return the original manuscripts:-)

The same Ptolemy issued the order that all ships arriving to Alexandria must be inspected and searched for books. All books found must be copied.

So we really lost a lot with Alexandrian library. When exactly it disappeared and how, is also subject to discussion. Some blame Julius Caesar who started a fire during a battle that destroyed a large part of the library. Other people say that it still existed at the time of the Arab conquest, and was destroyed by the conquerors. And many events in between are also mentioned.

The fact is that Claudius Ptolemy (astronomer, who probably worked in Alexandria in 2 century AD) could read Hipparchus. And we cannot. In fact almost all work in astronomy before Ptolemy is lost. And all work in mathematics before Euclid is lost.

We recently learned from secondary sources that there was highly developed combinatorics in the Hellenistic times (Habsieger, L.; Kazarian, M.; and Lando, S. "On the Second Number of Plutarch." Amer. Math. Monthly 105, 446, 1998). None of the original work survived.

We know the name of the great polymath Posidonius (135-51 BC) whose scientific output is comparable with that of Aristoteles. He wrote on all sciences. All his works are lost. Philosopher (logician) Chrysippus (279-206 BC) was regarded by contemporaries higher than Aristoteles. None of his works survived. None of the works of the founder of scientific medicine, Herophilos (335-280), survived. The great engineer (mechanic, hydraulic, pneumatic) Ctesibius (3d century BC) is credited for many inventions. All his work is lost.

Several sources frequently mention enormous warships of Hellenistic era (Tesserakonteres, Leontophoros are the largest mentioned) whose crew could exceed the crew of modern aircraft carrier. Historians speculate for the last 2000 years how these ships looked and how could they be constructed. No clear description survives.

REMARK for a mathematician. What we know of mathematics before 300 BC mostly comes from Euclid. Imagine that from our contemporary period only Bourbaki books survive...

REMARK 2. There is a consensus among modern scientists that Democritus of Abdera was one of the greatest scientists who ever lived.

Here is the list of all of the works of Democritus, with their titles as given by Diogenes Laertius: Great Cosmology; Little Cosmology; Cosmography; On the Planets; On Nature; On Human Nature; On Intelligence; On the Senses; On the Soul; On Flavors; On Color; On Diverse Movements of the Atoms; Of Changes in Shape; The Causes of Celestial Phenomena; The Causes of Atmospheric Phenomena; On Fire and On Things in Fire; The Causes of Acoustic Phenomena; Concerning the Magnet; The Causes of Seeds, Plants and Fruits; On Animals; A Description of the Sky; Geography; A Description of the Pole; On Geometry; Geometrical Reality; On the Tangents of the Circle and the Sphere; Numbers; On Irrational Lines and Solids; Projections; Astronomy; Astronomical Table; On Rays of Light; On Reflected Images; On Rhythm and Harmony; On Poetry; On the Beauty of Song; On Euphony and Cacophony; Concerning Homer, or on Correct Epic Diction; The Science of Medicine; On Agriculture; On Words; On Names; On Values, or On Virtue; On the Disposition which Characterizes the Wise; On Painting; A Treatise on Tactics; Circumnavigation of the Ocean; On History; The Thought of Chaldea; The Thought of the Phrygians; On the Sacred Writings of Babylon; On the Sacred Writings of Meroe; On Fevers and the Coughs Deriving from Illness; On Aporiae; Legal Questions; Pythagoras; On Logic, or Criterion of Thought; Confirmations; Points of Ethics; On Well-being. All lost …

  • Thanks for this very interesting answer. Could you elaborate a bit on this aspect: level of development in some areas of mathematics in Hellenistic time was not really surpassed until XIX century. I am also a mathematician, and I confirm this. I seem to remember that medieval (Indian, Persian, Chinese, Islamic) and early modern mathematics made substantial progress in algebra, calculus, number theory, statistics, (etc.) which affected basically every other branch of mathematics and to which the relatively crude understanding of Hellenistic mathematicians could not even come close. – 0range Oct 29 '18 at 16:34
  • 1
    @Orange: The space allowed here for comments does not allow me to write much, but I strongly recommend the book and papers of Lucio Russo, who systematically addresses exactly this topic. It is easy to argue that until the end of 19 century even Euclid was not fully digested, not speaking of Archimedes and Apollonius. Rigorous theory of real numbers was constructed only in the end of 19 century. While the Hellenistic Greeks had their theory of proportion, clumsy and complicated, of course, but EQUIVALENT to the theory of real numbers, and completely rigorous. – Alex Oct 29 '18 at 23:22
  • @Orange: There is no doubt that Archimedes knew that every Pell's equation has integer solutions. This theorem was proved by Lagrange in the modern times. See "Archimedes cattle problem" on Wikipedia. – Alex Oct 30 '18 at 0:05

The Serapeum is actually a smaller "branch" of the original library, formally part of the Temple of Serapis. The temple was converted to a Christian church by Theophilus around 390 AD, and it appears this is the reference you have noted above. This "branch" was not actually destroyed, but there is no doubt that many documents were destroyed during the conversion.

The official library, known as the Royal Library of Alexandria, was much larger and housed over half a million documents at the height of its glory. There are three different claims to having destroyed the original library, but we may never know exactly who was responsible.


What knowledge may have been lost at the Library of Alexandria?

The library at Alexandria was said to be one of the largest and most significant libraries of the ancient world. At it's peak the Library contained between 40,000 and 400,000 manuscripts, (scrolls) and employed more than 100 staff to maintain the collection. While it's true that their was no single catastrophe or fire which took out the entire collection but rather the institution declined and eroded over time like the empires it belonged too. We can still speak of what lost treasures may have once been perserved in that collection.

The Library of Alexandria
one of the largest and most significant libraries of the ancient world. The Library was part of a larger research institution called the Mouseion, which was dedicated to the Muses, the nine goddesses of the arts.[10] The idea of a universal library in Alexandria may have been proposed by Demetrius of Phalerum, an exiled Athenian statesman living in Alexandria, to Ptolemy I Soter, who may have established plans for the Library, but the Library itself was probably not built until the reign of his son Ptolemy II Philadelphus. The Library quickly acquired a large number of papyrus scrolls, due largely to the Ptolemaic kings' aggressive and well-funded policies for procuring texts. It is unknown precisely how many such scrolls were housed at any given time, but estimates range from 40,000 to 400,000 at its height.

Many important scholars worked there over the centuries.

The Library of Alexandria

  • Zenodotus of Ephesus, who worked towards standardizing the texts of the Homeric poems;
  • Callimachus, who wrote the Pinakes, sometimes considered to be the world's first library catalogue;
  • Apollonius of Rhodes, who composed the epic poem the Argonautica;
  • Eratosthenes of Cyrene, who calculated the circumference of the earth within a few hundred kilometers of accuracy;
  • Aristophanes of Byzantium, who invented the system of Greek diacritics and was the first to divide poetic texts into lines;
  • Aristarchus of Samothrace, who produced the definitive texts of the Homeric poems as well as extensive commentaries on them.
  • Archimedes is said to have invented the Archimedes screw, and early water pump used for irrigation while studying at the Library of Alexandria.

While no compressive Index of Alexandria's lost manuscripts exists, we can safely attribute some if not many of the known lost texts of antiquity to the contents of that library. They Include:

Lost Works

  • Agatharchides':
    • Ta kata ten Asian (Affairs in Asia) in 10 books,
    • Ta kata ten Europen (Affairs in Europe) in 49 books
    • Peri ten Erythras thalasses (On the Erythraean Sea) in 5 books
  • Agrippina the Younger:
    • Casus suorum (Misfortunes of her Family - memoir)
    • Sulpicius Alexander's Historia.
    • Anaxagoras' book of philosophy—only fragments of the first part have survived.
    • Apollodorus of Athens
    • Chronicle (Χρονικά), a Greek history in verse
    • On the Gods (Περὶ θεῶν), known through quotes to have - included etymologies of the names and epithets of the gods
    • A twelve-book essay about Homer's Catalogue of Ships Archimedes'
    • On Sphere-Making
    • On Polyhedra
    • Aristarchus of Samos' astronomy book outlining his heliocentrism (astronomical model in which the Earth and planets revolve around a relatively stationary Sun)
  • Aristotle's
    • second book of Poetics, dealing with comedy
    • On the Pythagoreans1
    • Protrepticus (fragments survived)
  • Augustus:
    • Rescript to Brutus Respecting Cato
    • Exhortations to Philosophy
    • History of His Own Life
    • Sicily (a work in verse)
    • Epigrams
    • Berossus' Babyloniaca (History of Babylonia)
  • Gaius Julius Caesar's
    • Anticatonis Libri II (only fragments survived)
    • Carmina et prolusiones (only fragments survived)
    • De analogia libri II ad M. Tullium Ciceronem De astris liber
    • Dicta collectanea ("collected sayings", also known by the Greek title άποφθέγματα) Letters (only fragments survived)
    • Epistulae ad Ciceronem
    • Epistulae ad familiares Iter (only one fragment survived)
    • Laudes Herculis
    • Libri auspiciorum ("books of auspices", also known as Auguralia) Oedipus
  • other works:
    • contributions to the libri pontificales as pontifex maximus
    • possibly some early love poems
  • Callinicus
    • Against the Philosophical Sects On the Renewal of Rome
    • Prosphonetikon to Gallienus, a salute addressed to the emperor
    • To Cleopatra, On the History of Alexandria, most likely dedicated to Zenobia, who claimed descent from Cleopatra
    • To Lupus, On Bad Taste on Rhetoric
  • Callisthenes'
    • An account of Alexander's expedition
    • A history of Greece from the Peace of Antalcidas (387) to the Phocian war (357)
  • A history of the Phocian war
  • Cato the Elder's:
    • Origines, a 7 book history of Rome and the Italian states.
    • Carmen de moribus, a book of prayers or incantations for the dead in verse.
    • Praecepta ad Filium, a collection of maxims.
    • A collection of his speeches.
  • Quintus Tullius Cicero's:
    • Four tragedies in the Greek style: Tiroas, Erigones, Electra, and one other.
  • Hortensius, a dialogue also known as "On Philosophy".
  • Consolatio, written to soothe his own sadness at the death of his daughter Tullia
  • Claudius'
    • De arte aleae ("the art of playing dice", a book on dice games)
    • an Etruscan dictionary
    • an Etruscan history
    • a history of Augustus' reign
    • eight volumes on Carthaginian history
    • a defense of Cicero against the charges of Asinius Gallus Ctesibius
    • On pneumatics, a work describing force pumps
    • Memorabilia, a compilation of his research works
  • Ctesias':
    • Persica, a history of Assyria and Persia in 23 books.
    • Indica, an account of India Eratosthenes
    • Περὶ τῆς ἀναμετρήσεως τῆς γῆς (On the Measurement of the Earth; lost, summarized by Cleomedes)
    • Geographica (lost, criticized by Strabo)
    • Arsinoe (a memoir of queen Arsinoe; lost; quoted by - Athenaeus in the Deipnosophistae) Euclid's
  • Conics, a work on conic sections later extended by
  • Apollonius of Perga into his famous work on the subject.
  • Porisms, the exact meaning of the title is controversial (probably "corollaries").
  • Pseudaria, or Book of Fallacies, an elementary text about errors in reasoning. Surface Loci concerned either loci (sets of points) on surfaces or loci which were themselves surfaces.
  • Eudemus':
  • History of Arithmetics, on the early history of Greek arithmetics (only one short quote survives)
  • History of Astronomy, on the early history of Greek astronomy (several quotes survive)
  • History of Geometry, on the early history of Greek geometry (several quotes survive)
  • Verrius Flaccus':
  • De Orthographia: De Obscuris Catonis, an elucidation of obscurities in the writings of Cato the Elder
  • Saturnus, dealing with questions of Roman ritual Rerum memoria dignarum libri, an encyclopaedic work much used by Pliny the Elder Res Etruscae, probably on augury.
  • Frontinus:
    • De re militari, a military manual
  • Gorgias':
    • On Non-Existence (or On Nature) - Only two sketches of it exist.
    • Epitaphios - What exists is thought to be only a small fragment of a significantly longer piece.
  • The Hesiodic Catalogue of Women
  • Homer's Margites.
    • The Odyssey mentions the blind singer Demodocus performing a poem recounting the otherwise unknown "Quarrel of Odysseus and Achilles", which might have been an actual work that did not survive
  • Livy: 107 of the 142 books of Ab Urbe Condita, a history of Rome
  • Longinus:
  • On The End: by Longinus in answer to Plotinus and Gentilianus Amelius (preface survives, quoted by Porphyry)
    • On Impulse
    • On Principles
    • Lover of Antiquity
    • On the Natural Life
    • Difficulties in Homer
    • Whether Homer is a Philosopher
    • Homeric Problems and Solutions
    • Things Contrary to History which the Grammarians Explain as Historical
    • On Words in Homer with Multiple Senses
    • Attic Diction
    • Lexicon of Antimachus and Heracleon
  • Lucan's:
    • Catachthonion
    • Iliacon from the Trojan cycle
    • Epigrammata
    • Adlocutio ad Pollam
    • Silvae
    • Saturnalia
    • Medea
    • Salticae Fabulae
    • Laudes Neronis, a praise of Nero
    • Orpheus
    • Prosa oratio in Octavium Sagittam
    • Epistulae ex Campania
    • De Incendio Urbis
    • Manetho's Ægyptiaca (History of Egypt) in 3 books. Only few fragments survive.
    • Memnon of Heraclea's history of Heraclea Pontica.
  • Nicander's:
    • Aetolica, a prose history of Aetolia.
    • Heteroeumena, a mythological epic.
    • Georgica and Melissourgica, of which considerable - fragments are preserved.
    • Ovid's poem Medea, of which only two fragments survive.
    • Pamphilus of Alexandria's comprehensive lexicon in 95 books of foreign or obscure words.
  • Pherecydes of Leros:
    • A history of Leros
    • an essay, On Iphigeneia
    • On the Festivals of Dionysus
    • Genealogies of the gods and heroes, originally in ten books; numerous fragments have been preserved.
    • Pherecydes of Syros' Heptamychia
    • Philo of Byblos' Phoenician History, a Greek translation of the original Phoenician book attributed to Sanchuniathon.Considerable fragments have been preserved, chiefly by Eusebius in the Praeparatio evangelica (i.9; iv.16)
  • Pliny the Elder's:
    • History of the German Wars, some quotations survive in Tacitus' Annals and Germania
  • Studiosus, a detailed work on rhetoric
    • Dubii sermonis, in eight books
    • History of his Times, in thirty-one books, also quoted by Tacitus.
    • De jaculatione equestri a military handbook on missiles thrown from horseback.
    • Gaius Asinius Pollio's Historiae ("Histories")
  • Alexander Polyhistor's Successions of Philosophers.
  • Porphyry:
  • Ad Gedalium (a commentary on Aristotle's Categories in seven books
  • Against the Christian (only fragments survive) Praxagoras's History of Constantine the Great (known from a précis by Photius).
  • Prodicus':
    • On Nature
    • On the Nature of Man
    • "On Propriety of Language"
    • On the Choice of Heracles
  • Protagoras':
    • "On the Gods" (essay)
    • On the Art of Disputation
    • On the Original State of Things
    • On Truth
  • Pytheas of Massalia's τὰ περὶ τοῦ Ὠκεανοῦ (ta peri tou Okeanou) "On the Ocean".
  • Quintilian's De Causis Corruptae Eloquentiae (On the Causes of Corrupted Eloquence)
    • Septimius Severus' autobiography
    • Diodorus Siculus' Bibliotheca historia (Historical Library)- of 40 books, only the first 5 books, and books 10 through 20 are extant.
    • The Hellespontine Sibyl's Sibylline Books
    • Seneca the Younger book on signs. 5000 were compiled
    • Socrates' verse versions of Aesop's Fables. Speusippus On Pythagorean Numbers
    • Strabo's History. Suetonius'
    • De Viris Illustribus ("On Famous Men" — in the field of literature), to which belongs: De Illustribus Grammaticis ("Lives Of The Grammarians"), De Claris Rhetoribus ("Lives Of The Rhetoricians"), and Lives Of The Poets. Some fragments exist.
    • Lives of Famous Whores
    • Royal Biographies
    • Roma ("On Rome"), in four parts: Roman Manners & Customs, The Roman Year, The Roman Festivals, and Roman Dress.
    • Greek Games
    • On Public Offices
    • On Cicero’s Republic
    • The Physical Defects of Mankind
    • Methods of Reckoning Time
    • An Essay on Nature
    • Greek Terms of Abuse
    • Grammatical Problems
    • Critical Signs Used in Books
    • Sulla's Memoirs, referenced by Plutarch
    • Thales
    • On the Solstice (possible lost work)
    • On the Equinox (possible lost work)
  • Tiberius
    • Autobiography ("brief and sketchy," per Suetonius
    • Trajan's Dacica (or De bello dacico) Varro
    • Saturarum Menippearum libri CL or Menippean Satires in 150 books
    • Antiquitates rerum humanarum et divinarum libri XLI
    • Logistoricon libri LXXVI
    • Hebdomades vel de imaginibus
    • Disciplinarum libri IX
  • Zenobia:
    • Epitome of the history of Alexandria and the Orient (according to the Historia Augusta)
  • The work of the Cyclic poets (excluding Homer), specifically:
    • six epics of the Epic Cycle: Cypria, Aethiopis, the - Little Iliad, the Iliupersis ("Sack of Troy"), Nostoi ("Returns"), and Telegony.
    • four epics of the Theban Cycle: Oedipodea, Thebaid, Epigoni (epic), and Alcmeonis.
    • other early Greek epics: Titanomachy, Heracleia, Capture of Oechalia, Naupactia, Phocais, Minyas



Of the works written by Euclid, perhaps the most famous Greek philosopher, we have six and have lost six, 50%. For Archimedes we have about 10 works and lost perhaps around 20, a survival rate of 1/3. For the playright Euripides we have 19 plays and have lost about 60 plays, a survival rate of 25%. For other famous authors and scientists there are similar percentages.

It is probably safe to assume that the libraries at Alexandria originally had multiple copies of all of these works.


If the only copy of a work was in one specific library - it was already lost.

In our hurry to reduce history to simple narratives, often the most obvious observations get lost. If the only copy of, say, Aristotle's "Exhortation to Philosophy" was lost to a specific disaster in the Alexandrian library, then clearly the work had already lost its relevance in that world. The more important question is, "Why did so many works from authors that we esteem today perish during Late Antiquity?" The answer cannot be that one specific library in one specific city was destroyed. It is obviously a much more complex question that offers opportunity for rich speculation and research.

(Actually, it's two questions, isn't it? For the flip side of the question is, "Why do we treasure these works that apparently the people of Late Antiquity didn't feel were worth preserving?!")

  • 2
    Sources would improve this answer. I'm not sure that the assertion in your first paragraph will stand to scrutiny against the cost of preparing hand copies of obscure works. – Mark C. Wallace Oct 25 '18 at 17:50
  • 1
    @Mark C. Wallace The statement is almost a tautology, isn't it? But simply consider the profusion of Neoplatonist texts available vs. the paucity of texts from Aristotle, et al. It is almost beyond dispute that the late Classical age was far more interested in mystical speculation than in natural philosophy. The burning of the Library is just a footnote to that larger story. – pokep Oct 28 '18 at 16:52
  • This is an excellent point. Books aren't saved by being in libraries, they're saved by being copied. (The half-life of ancient manuscripts was probably less than a century.) The ancient texts that survived have been copied and recopied (and frequently translated) over the centuries. – Mark Olson Feb 9 at 16:35

Which destruction did the damage (or the most damage)? As Wikipedia notes:

Despite the widespread modern belief that the Library was "burned" once and cataclysmically destroyed, the Library actually declined gradually over the course of several centuries, starting with the purging of intellectuals from Alexandria in 145 BC during the reign of Ptolemy VIII Physcon, which resulted in Aristarchus of Samothrace, the head librarian, resigning from his position and exiling himself to Cyprus. Many other scholars, including Dionysius Thrax and Apollodorus of Athens, fled to other cities, where they continued teaching and conducting scholarship. The Library, or part of its collection, was accidentally burned by Julius Caesar during his civil war in 48 BC, but it is unclear how much was actually destroyed and it seems to have either survived or been rebuilt shortly thereafter; the geographer Strabo mentions having visited the Mouseion in around 20 BC and the prodigious scholarly output of Didymus Chalcenterus in Alexandria from this period indicates that he had access to at least some of the Library's resources.

The Library dwindled during the Roman Period, due to lack of funding and support. Its membership appears to have ceased by the 260s AD. Between 270–275 AD, the city of Alexandria saw a rebellion and an imperial counterattack that probably destroyed whatever remained of the Library, if it still existed at that time. The daughter library of the Serapeum may have survived after the main Library's destruction. The Serapeum was vandalized and demolished in 391 AD under a decree issued by Coptic Christian Pope Theophilus of Alexandria, but it does not seem to have housed books at the time and was mainly used as a gathering place for Neoplatonist philosophers following the teachings of Iamblichus.

Whatever institution still existed in the 640s was suppressed at least one more time by Caliph Omar.

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