The Lamps of Leyden: On Two Students and the Art of Forgetting

Every fall, as students return to their libraries and professionals to their digital workspaces, the conversation invariably turns to how we might better capture and keep what we learn. We install new apps, perfect our Zettelkasten techniques, and vow to build a second brain that never forgets. The underlying anxiety is ancient: the fear that a valuable insight, once lost, is lost forever. We are all scribes, frantically illuminating manuscripts against the coming dark.

This makes the story of two young men in 17th-century Leiden all the more jarring. They were students of the great humanist scholar Daniel Heinsius, a man whose library and learning were said to be boundless. The two pupils, whose names are lost to us, shared a room, a passion for classical texts, and a peculiar form of study. They would spend their days in the university library, consuming all they could. But at night, in their small room lit by a single lamp, they did something that would horrify the modern knowledge worker: they systematically tried to forget.

Their method, as recounted in scattered letters, was a kind of intellectual purging. After a day of reading, one student would begin to recite everything he had absorbed—arguments from Cicero, a new astronomical theory, a complex Latin verse. The other’s sole task was to listen and then argue against it, not to refine the ideas, but to dismantle them. They would pick apart the logic, question the sources, and deliberately confuse the details until the original thought was mangled beyond recognition. The goal wasn't clarification; it was disintegration. They called these sessions "blowing out the lamp" on a thought, extinguishing it so a new one could be lit the next day.

To our data-hoarding sensibilities, this seems like madness, a wanton destruction of intellectual capital. But I think they understood something we have forgotten in our quest for total recall: that a mind, like a field, must sometimes lie fallow. Our digital feeds and note-taking systems are engineered for accumulation, creating a relentless pressure to preserve. We build archives of everything we’ve ever read, but we rarely create the cognitive space necessary for truly new ideas to form. The clutter of captured thoughts can become a prison, forcing us to constantly revisit and reorganize rather than synthesize and transcend.

The Space Cleared by Forgetting

The students of Leyden were not advocating for ignorance. Their nightly rituals were an act of supreme confidence in their ability to learn anew, and a profound skepticism toward the permanence of any single day’s findings. They trusted the process of learning more than the product. By willingly letting go of the specific formulations, they made room for deeper patterns and more robust connections to emerge organically, freed from the tyranny of the exact quote or the perfectly filed note.

This is the forgotten art we might consider reclaiming. Not the wholesale deletion of our digital gardens, but perhaps the deliberate practice of pruning, not for efficiency, but for respiration. What if we occasionally closed a notebook without transcribing its contents? What if we allowed a brilliant article to fade from memory, trusting that if its core truth was essential, it would find its way back to us in a more durable form? The lamps of Leyden remind us that the ultimate act of curation might not be what we choose to keep, but what we courageously choose to let go, creating the empty space where genuine understanding, rather than mere information, can finally take root.

Notes & further reading

A few pages I came back to while writing this: