John IV, Duke of Brabant, wanted a university for his capital. In 1425 he persuaded Pope Martin V to issue the bull that created a studium generale at Leuven, modeled on Paris and Cologne. It opened with four faculties: arts, law, medicine, and from 1432 theology. Latin was the only language of instruction, and remained so for the entire 372 years of the institution's life. The first colleges were named for animals and household objects, a custom borrowed from Paris: the Castle, the Pig, the Lily, the Falcon. By the seventeenth century there were eighteen of them, scattered through the medieval streets. Students drank in the same taverns where students drink today. The geography of the modern KU Leuven still follows the footprint of these vanished colleges.

The faculty list reads like a roll call of the Northern Renaissance. Adriaan Floriszoon Boeyens taught here before he was elected Pope Adrian VI in 1522, the last non-Italian pope until John Paul II. Desiderius Erasmus inspired and guided the founding of the Collegium Trilingue in 1517 — established under the bequest of Hieronymus Busleyden — the first institution in Europe to teach Latin, Greek, and Hebrew together. Andreas Vesalius, who would write De humani corporis fabrica and effectively invent modern anatomy, took his medical degree at Leuven in 1537. Gerardus Mercator, whose 1569 projection is still how the world looks on a wall map, studied here in the 1530s. For about a hundred years in the sixteenth century, Leuven was where you went if you wanted to do something that mattered with your mind.

In 1640, two years after his death, Cornelius Jansen's massive theological work Augustinus was published in Leuven. The book argued for a strict Augustinian reading of grace and free will that sounded, to Rome, dangerously close to Calvinism. Jansen had been rector of the university and bishop of Ypres. His students stayed in Leuven and kept teaching. For the next 150 years the theology faculty was the European headquarters of Jansenism, even after three papal bulls explicitly condemned it. Zeger Bernhard van Espen, professor of canon law, gave away his entire salary to the poor and was eventually forced to flee to Holland for his views. He died in Amsterdam in 1728, faithful to the end to what one historian called the discipline and customs of the primitive church. His disciple Febronius would carry the same ideas into German lands and provoke a separate ecclesiastical crisis.

The Treaty of Campo Formio, signed October 17, 1797, ceded the Austrian Netherlands to France in exchange for Venice. Eight days later the Departement of the Dyle issued the closure decree. Library staff packed the most valuable manuscripts for Paris, where they joined the loot at the Bibliothèque Nationale. Lesser holdings went to the new Central School in Brussels. Some books, almost certainly, were quietly carried off by professors and saved that way. A new Catholic University of Leuven would open in 1835, after Belgian independence, in the same town, and it would claim continuity with the old institution. The claim was more sentimental than legal. The original university, founded by John IV and confirmed by a Renaissance pope, ended on a Wednesday in autumn when a French clerk read a decree aloud and went home. The archives that survived were inscribed by UNESCO on the Memory of the World Register in 2013.