Ask most people how the library of Alexandria ended and they will describe one terrible fire. The truth is slower and less dramatic. The library seems to have declined over centuries, through neglect, lost funding, political turmoil and several separate disasters, and some of the most famous stories about its destruction are probably false.

Caesar's fire, 48 BCE

In 48 BCE Julius Caesar intervened in a civil war between Cleopatra VII and her brother Ptolemy XIII and found himself besieged in Alexandria. To keep the enemy fleet from cutting him off, he set fire to ships in the harbor, and the fire spread to buildings near the docks. The Greek writer Plutarch, writing about 150 years later, says it destroyed the great library. The Roman philosopher Seneca mentions 40,000 books burned at Alexandria. The historian Cassius Dio says warehouses near the docks, holding grain and books, burned.

Many historians conclude that what burned were books stored in warehouses near the harbor, perhaps awaiting export or shelving, rather than the main library. The geographer Strabo worked in Alexandria about twenty years later and describes the Museum still operating, and scholars continued to work there. The fire was a real loss, but probably not the end.

Roman Alexandria

After Cleopatra's death in 30 BCE, Egypt became a Roman province. The Museum continued, now under the emperors, who appointed its members. The emperor Claudius added a new wing. But membership became increasingly an honor given to favorites, including athletes and officials, rather than a post for working scholars. Without the old royal passion for collecting, the collection probably shrank as scrolls decayed and were not recopied.

Some stories from this period also need caution. Plutarch reports a claim that Mark Antony gave Cleopatra 200,000 scrolls from the library of Pergamon to make up for losses in the fire. Plutarch himself says the claim came from a hostile witness and doubts that it was true. It is often repeated today as fact.

Aurelian, 272 CE

In the third century the Roman Empire was torn by civil wars. Alexandria fell for a time to forces of the queen Zenobia of Palmyra. When the emperor Aurelian retook the city around 272 CE, fighting devastated the Brucheion, the palace quarter where the Museum stood. The historian Ammianus Marcellinus later described that district as laid waste. Many historians think this is the most likely end of the main library and the old Museum.

The Serapeum, 391 CE

The daughter library at the Serapeum lasted longer. By the late fourth century the Roman Empire had become officially Christian, and the emperor Theodosius issued laws against pagan sacrifice. In 391 CE, Christians led by Theophilus, bishop of Alexandria, destroyed the Serapeum, one of the most famous temples in the world. Ancient accounts of the destruction do not clearly mention books, and it is uncertain whether much of a collection remained there by then. It was a grave blow to the city's pagan culture either way.

Hypatia, 415 CE

The philosopher and mathematician Hypatia, daughter of the mathematician Theon, taught in Alexandria and was widely respected. In 415 CE she was murdered by a Christian mob during a political feud involving the city's bishop and its Roman governor. Her death is often linked to the library in popular culture, but it had nothing to do with the library's destruction, which had largely happened long before. Her murder stands on its own as a crime against a person, a reminder that violence against thinkers is a different evil from the loss of books, and in some ways worse.

The Caliph Umar legend

The Arab conquest of Alexandria in 642 CE gave rise to the most famous story of all. In it, the general Amr ibn al-As asks the caliph Umar what to do with the library, and Umar replies that if the books agree with the Quran they are unnecessary, and if they disagree they are harmful, so they should be destroyed. The books are said to have fueled the city's bathhouses for six months. But the story first appears more than five hundred years after the conquest, in writers of the thirteenth century, and no earlier source mentions it. Most historians reject it. The English historian Edward Gibbon, writing in the 1780s, already doubted it.

Worked example: one fire or many?

Sort the claims about the library's end by how well supported they are.

• Strongly supported: fire near the harbor in 48 BCE destroyed many books; fighting under Aurelian devastated the palace quarter around 272 CE; the Serapeum temple was destroyed in 391 CE.
• Uncertain: whether the 48 BCE fire reached the main library; whether books remained in the Serapeum in 391.
• Probably false: Caliph Umar's order; any link between Hypatia's murder and the library's destruction.

Why do the false stories survive? Each serves someone's argument. The Umar story has been used against Islam, the Serapeum story against Christianity, and the Caesar story to dramatize the fall of the ancient world. A single villain makes a better tale than centuries of neglect. But the slow version carries a more useful warning: knowledge is usually lost not in one blaze but through years of underfunding, indifference and failure to make new copies.