Is a novel more like a military offensive, a bout of fatigue, a rule, a church, a diet, an obstacle, a friendship, a child, a world, a stew, a cathedral, a dress? In the final pages of Marcel Proust’s In Search of Lost Time, the narrator—surely here as much of an avatar of the author as he ever is—wrestles with the best comparison. One of these images has taken hold more than the others, perhaps because it seems most accurate to this novel in particular: the cathedral. “How many great cathedrals remain unfinished!” the narrator exclaims. It’s hard not to think mournfully of a dying Proust, that inveterate reviser unable to intervene in the final volumes of his monumental novel. We remember the looming and chronically incomplete cathedral and forget the other options.

But the cathedral is not actually the comparison that wins out in Time Regained, when the narrator envisions his future at a white wooden desk: “Pinning here and there an extra page, I should construct [or baste, bâtir] my book, I dare not say ambitiously like a cathedral, but quite simply like a dress.” Not like a cathedral, but like a dress. Not like stone, but like fabric. Not building, but basting. Not lasting, but provisional. Not ambitious, but simple. Not medieval, after all, but contemporary. Not fixed, but expansive—which perhaps applies to cathedrals, too. There is something more than a veneer of false humility to Proust’s sudden rejection of the cathedral in favor of the garment: Pinning and basting evokes text at its most textile. The word text comes, we know, from the Latin verb texere, to weave. The implication is that like cloth, the text can be materially manipulated in certain textile ways: unfurled, rewoven, thickened, patched, and stitched.

And it is so: When he at last gets to work, hundreds of pages later, the narrator describes his writing process as one of stitching and pasting (with the critical help of his family’s servant, Françoise). Marcel and Françoise collaborate to create the manuscript, with Marcel generating and inscribing the words and Françoise maintaining the object. He pastes extra bits onto his pages, which occasionally tear from its clumsy application or suffer under the attack of moths. That is when Françoise’s handiwork comes in handy, as she consolidates the pages “just as she stitched patches on to the worn parts of her dresses or as, on the kitchen window, while waiting for the glazier as I was waiting for the printer, she used to paste a piece of newspaper where a pane of glass had been broken.” Françoise’s restorative patchwork is vital but mysterious. What material repairs the copybooks, in parallel to the implied fabric for her dresses or the wordy translucent newspaper for the windows? Does she use scraps of paper? Or does she draw the holes and tears closed with her needle? The “best” parts, Françoise goes on to lament, are chewed up and digested not by readers, but by the moth or the author’s poor use of paste. The sticky, fragile, even infested draft needs repair and renewal with added material.

Adding extraneous stuff to a preexisting text is a practice with a name: interpolation. Proust is one of the most notorious interpolators in literary history. Like his fellow graphomaniac Montaigne, he could not resist inserting new material into his drafts and exceeding the bounds of his writing surface and pasting on scraps of paper to make room for the wanderings of his sinuous sentences. The narrator’s textile writing process seems to mirror his.

Etymologically, interpolation means “to place among” (from the Latin prefix inter + verb polire). Like the word text, it too stems from the world of textiles. In its earliest usage, it described the process of fulling, in which fabric is thickened and refined. Over time, the Latin verb interpolare, from which our noun derives, came to refer to patching cloth and, more infamously, texts. Interpolators insert later material into a preexisting work. Since antiquity, philologists have decried the harmful effect of interpolation on textual authority and purity, marking later insertions as spurious and excising them whenever possible. Proust knew about this negative technical connotation. In The Captive, he writes of learning of Swann’s death as an experience akin to encountering a distracting interpolation: “It was the same death whose striking and specific strangeness had recurred to me one evening when, as I ran my eye over the newspaper, my attention was suddenly arrested by the announcement of it, as though traced in mysterious lines interpolated there out of place [inopportunément].” Scott Moncrieff’s tepid “out of place” doesn’t quite capture the negativity of the French adverb: Proust is clear that the lines whose mystery finds an echo in the death announcement are interpolated unfortunately or at the wrong time. He intimates that interpolation is intrusive and unsettling in a way that has to do not only with textual authenticity but also with time. Although he knew about interpolation’s bad reputation in manuscript contexts, Proust exploits its latent temporal quality. His writing process, with all its pins, paste, and “paperies,” craftily reproduces the centrality of interpolation to his conception of time.

Despite portraying his manuscript as susceptible to patching, like a dress, the allure of the bookish cathedral as a metaphor for the novel never quite dissipates. Perhaps that is because it’s hard to read the Search and not be struck by the references to the Middle Ages. The great medievalist Michel Zink winkingly called Proust’s engagement with the medieval a “voluntary memory,” in distinction from the involuntary memories that tunnel back to past time and bring it surging into the present. Church porches, stained glass, castles, books of hours, knights, and statues crowd the narrator’s imagination. The medieval can even be interpolated into the physical world. In Swann’s Way, the narrator marvels at how Françoise incarnates a medieval peasant, and the butcher’s boy in Combray replicates a statue from the portal of the nearby church, Saint-André-des-Champs (modeled in part on the real Romanesque church Saint-Loup-de-Naud). The same displaced incarnation can go in reverse, as when a stone saint on the same portal represents a 19th-century woman:

There, too […] stood a saint with the full cheeks, the firm breasts that swelled out her draperies like a cluster of ripe grapes inside a horsehair sack, the narrow forehead, short and stubborn nose, deep-set eyes, and the strong, unemotional, courageous expression of the peasant women of these parts.

The past and the present don’t just resemble each other, they duplicate each other. There is no rupture: Medieval noses persist on present faces. The past penetrates the present.

But the Middle Ages is not just one past among many that intrude into the lived experience of the novel. It’s also the period in which interpolation became the critical form for thinking about time that it remains for Proust.

Medieval revisers intervened in their stories of the past to suggest different ways that human experience might relate to time. Through interpolation, histories accommodate all kinds of unexpected material. In the most egregious example from French histories, a scribe takes advantage of 12 years of peace during King Arthur’s reign to insert five whole romances about the adventures of his knights. (The manuscript is Bibliothèque nationale de France, fr. 1450; this history, the Norman cleric Wace’s Roman de Brut, translated from Latin in 1155.) In the history, King Arthur was betrayed by his steward Mordred. (In later traditions, Mordred becomes Arthur’s incestuous son; but in this version, he’s simply Arthur’s nephew.) Around 1176, in full awareness of the widely circulating story of Mordred, the French poet Chrétien de Troyes wrote a treacherous regent into his Arthurian tale Cligès, which is one of the romances inserted into the Brut in this manuscript. Unlike Mordred, Angrès is defeated by Arthur and his champion Alexandre, allowing him to keep his throne and continue providing for an adventure-hungry coterie of knights. This manuscript sinuously integrates Chrétien’s rewriting into the history that inspired it: A reader of this history sees Arthur betrayed by Chrétien’s usurper Angrès before his reign is imperiled by Mordred.

This interpolation doesn’t just make the history longer or (to our eyes) more fictitious. It also creates a typological pattern, changing the time scheme of the history from something approximating that old chestnut “one damn thing after another” to one where figures and events might prefigure subsequent ones or fulfill the promise of previous ones. The manuscript circles around the idea of treachery. Its repetitions bring Arthur’s past in contact with his present, and the new iteration produces a different outcome. Other medieval historians used interpolation as a way to approximate divine eternity, in Augustine’s idea of it as a totalizing “now.” Collapsing past, present, and future, the illustrator of an odd little manuscript called the Egerton Brut (British Library Egerton 3028, ca. 1338) referred to multiple moments in a single illumination in an attempt to evade duration and simulate divine simultaneity.

It’s unlikely that Proust knew of these medieval experiments in how to represent and understand time. But it’s nevertheless striking that a novel so invested in the persistence of the Middle Ages found its way back to that lost time in searching for its own. Like the “transposed sensations” that are themselves interpolated into lived experience, interpolation is an unwilled reflex for Proust. The medieval is an involuntary memory after all.

In Time Regained, the narrator locates the truth that his senses involuntarily reveal to him in an inner manuscript, as open to interpolation as medieval histories. The sensations of taste, sound, and vision that constitute lost time are “un grimoire compliqué et fleuri”—a “magical scrawl, complex and elaborate,” as Scott Moncrieff’s posthumous successor Andreas Mayor has it, but perhaps better translated as an “intricate and flowery spell-book.” The inscrutable, magical book is illuminated by the floriate borders of manuscripts. And this inner book of enchantments, or catalogue of sensations, awaits discovery and perusal by the narrator, like a manuscript in an unreadable script. He goes on, “As for the inner book of unknown symbols (symbols carved in relief they might have been, which my attention, as it explored my unconscious, groped for and stumbled against and followed the contours of, like a diver exploring the ocean-bed), if I tried to read them no one could help me with any rules, for to read them was an act of creation in which no one can do our work for us or even collaborate with us.”

Cryptic and illegible, the impossible inner book is a three-dimensional, reeflike Voynich manuscript. Its “unknown symbols” are the impressions made by the ideas that arise through living, not through thinking. But for all its obscurity and its unplanned formation through sensory experience, this manuscript is of singular importance: In it, Proust locates the source of all creativity, and indeed of all literature. To read it is to participate in lawless and independent creation. I translate: “The book with its figured letters, not traced by us, is our only book.” “Figured letters” is a confusing phrase in any context other than that of medieval manuscripts, where illuminated and inhabited initials made by long-ago artists beckon. The self is not just any book: It is a unique manuscript requiring decryption and translation.

Is the novel like a cathedral or a dress? Perhaps the question itself is a misdirection.

If memory is contained in a medieval manuscript, as Proust posits in these passages, then interpolation becomes a particularly apt metaphor for the involuntary memories, or “transposed sensations,” critical to the finding of lost time. The famous taste of the madeleine, the less famous stumble on uneven flagstones, the even less famous stiff napkin dabbing the mouth and tinkle of a spoon on a saucer all interpolate the narrator’s present day and bring the past surging back through the network of memory they invoke through their sensory echoes. The instability and variety inherent in these moments of interpolation produce not just art, but a new kind of time, a paradoxically extratemporal “time in the pure state” where past, present, and future collapse into one another. Proust reaches for eternity through the wormhole of interpolation, just as had the 14th-century scribe of the Egerton Brut.

Proust makes interpolation into an object of longing but also warns that it can be a mechanism of distortion. In The Fugitive, taking stock of his period of grief after the death of his lover Albertine, the narrator speaks of his continued wish “to repair lost time,” suggesting that time is susceptible to patching, if only he could find a way to do it. In the same breath, he says that his memory resembles the moth-eaten manuscript that Françoise will later repair. It is punctuated by the “empty space” of oblivion, which, “by its fragmentary, irregular interpolation in my memory—like a thick fog at sea that obliterates all the landmarks—confused, dislocated my sense of distances in time, contracted in one place, extended in another, and made me suppose myself now farther away from things, now far closer to them than I really was.” Interpolation here figures not the patches of involuntary memory, but the intrusive holes of lost time. It is a distorting fog, temps in the sense of weather. Forgetting causes uncertainty about the scale of time. Even when it is composed of absences or gaps, interpolation retains the generative possibilities of dislocation for bringing the past back whose power the narrator will realize only years later, crossing a courtyard on the way to a party.

Toward the end of the novel, when introduced to her at a party, Proust breathlessly shows how Mlle de Saint-Loup—daughter of his long-time friends Robert and Gilberte—is the star-like intersection of the many worlds and people of the novel. Musing on this woman as a human crossroads, the narrator suddenly changes metaphors, from map to fabric. Life “is perpetually weaving fresh threads which link one individual and one event to another, and … these threads are crossed and recrossed, doubled and redoubled to thicken the web, so that between any slightest point of our past and all the others a rich network of memories gives us an almost infinite variety of communicating paths to choose from.” Like a fuller, the original interpolator, life thickens the weave among people and events. Disruptive and restorative, interpolation is the paradoxical form of life, literature, and time itself.

Is the novel like a cathedral or a dress? Perhaps the question itself is a misdirection. The narrator draws the two together on a walk with Swann’s fashionable wife, Odette, in Within a Budding Grove. Should Odette feel too warm and give the adolescent Marcel her jacket,

in the sleeves of the jacket that lay folded across my arm I would see, and would lengthily gaze at, for my own pleasure or from affection for its wearer, some exquisite detail, a deliciously tinted strap, a lining of mauve satinette that, ordinarily concealed from every eye, was yet just as delicately fashioned as the outer parts, like those Gothic carvings on a cathedral, hidden on the inside of a balustrade eighty feet from the ground, as perfect as are the bas-reliefs over the main porch, and yet never seen by any living man until, happening to pass that way on his travels, an artist obtains leave to climb up there among them, to stroll in the open air, overlooking the whole town, between the soaring towers.

Odette’s toilette shares with cathedrals the art of details revealed only by special permission. The privileged narrator examines the concealed lining as the traveling artist, alone among the living, admires the perfection of the sculpted cathedral roof. The jacket lends its soft interior to the cathedral as the building offers its stony monumentality to the toilette. Dress and cathedral both have their secrets and their voyeurs. And both, we might imagine, inscribe in the inner manuscript the feeling of the open air, ready to be interpolated by a passing breeze.