The story of how ancient texts survived to the present day is as much a story of destruction and loss as of preservation — and understanding what didn't survive is essential to understanding the limitations of our knowledge of antiquity.

The primary mechanism of text survival was hand-copying by medieval monks in Western Europe and by Byzantine scholars in the East. A text survived only if it was copied repeatedly over centuries; the copyists' choices (what to copy, what to let fall out of the copying chain) shaped which ancient texts we have. The taste of medieval copyists ran toward certain genres — Christian apologetics, classical rhetoric, Virgil — and away from others. We have one play by Menander, perhaps the most popular playwright of antiquity; we have all 37 of Shakespeare's plays.

The Arabic translation movement of the 8th–10th centuries AD preserved substantial portions of ancient Greek scientific and philosophical texts — many by Aristotle, works of ancient mathematics and medicine — that would otherwise have been lost entirely. The transmission of Greek science to the medieval Islamic world and then back to medieval Europe via Latin translation is one of the great arcs of cultural history.

Particular catastrophes — the burning of Carthage's library, the destruction of Alexandria's collections, the Fourth Crusade's sack of Constantinople, the fires set by the Aztec-burning Spanish — ended preservation chains that had persisted for centuries. But the losses from these dramatic events were probably smaller than the cumulative loss from simple neglect: texts not copied because no one wanted them, rotting in damp storage, discarded to make way for newer acquisitions.