Like every graduate student, I once holed up in the library cramming for my doctoral oral exams. This ritual hazing starts with a long reading list. Come exam day, the scholar must prove mastery of a field, whether it’s Islamic art or German history. The student sits before a panel of professors, answering questions drawn from the book list.
To prepare for this initiation, I bought a lifetime supply of index cards. On each four-by-six rectangle, I distilled the major points of a book. My index cards—portable, visual, tactile, easily rearranged and reshuffled—got me through the exam.
Yet it never occurred to me, as I rehearsed my talking points more than a decade ago, that my index cards belonged to the very European history I was studying. The index card was a product of the Enlightenment, conceived by one of its towering figures: Carl Linnaeus, the Swedish botanist, physician, and the father of modern taxonomy. But like all information systems, the index card had unexpected political implications, too: It helped set the stage for categorizing people, and for the prejudice and violence that comes along with such classification.
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In 1767, near the end of his career, Linnaeus began to use “little paper slips of a standard size” to record information about plants and animals. According to the historians Isabelle Charmantier and Staffan Müller-Wille, these paper slips offered “an expedient solution to an information-overload crisis” for the Swedish scientist. More than 1,000 of them, measuring five by three inches, are housed at London’s Linnean Society. Each contains notes about plants and material culled from books and other publications. While flimsier than heavy stock and cut by hand, they’re virtually indistinguishable from modern index cards.
The Swedish scientist is more often credited with another invention: binomial nomenclature, the latinized two-part name assigned to every species. Before Linnaeus, rambling descriptions were used to identify plants and animals. A tomato, for example, was a mouthful: Solanum caule inermi herbaceo foliis pinnatis incisis. After Linnaeus, the round fruit became Solanum lycopersicum. Thanks to his landmark study, Systema Naturae, naturalists had a universal language, which organized the natural world into the nested hierarchies still used today—species, genus, family, order, class, phylum, and kingdom.
In 18th-century Europe, Linnaeus became a household name. “Tell him I know no greater man on earth,” said Jean-Jacques Rousseau of his Swedish idol. Like other savants of his day, Rousseau saw the study of plants as a moral pursuit, a virtuous escape into nature. Germany’s man of letters, Johann Wolfgang von Goethe, confessed that after Shakespeare and Spinoza, no one had influenced him more than Linnaeus. “God created—Linnaeus arranged,” went the adage.
But despite his meteoric success, Linnaeus had a problem. The man who made order from nature’s chaos did not have a good management system for his own work. His methods for sorting and storing information about the natural world couldn’t keep up with the flood of it he was producing. Linnaeus’s appearance only added to an aura of disorder. Stunned visitors described the prince of botany as a “markedly unshaven” man in “dusty shoes and stockings.” Writing about himself, Linnaeus was even less charitable: “Brow furrowed. A low wart on the right cheek and another on the right side of the nose. Teeth bad, worm-eaten.”
Worms aside, the real issue vexing Sweden’s top scientist was how to manage a data deluge. He had started out collecting plants in the woods of his native southern Sweden. But as his profile grew, so did his research and writing, and the number of students under his wing. Achieving scientific renown of their own, Linnaeus’s students sent him specimens from their travels in Europe, Russia, the Middle East, West Africa, and China. According to Charmantier and Müller-Wille, most botanists of the era employed a team to manage their affairs that would keep track of correspondence and categorize specimens. But not Linnaeus, “who preferred to work alone.” Starting in the 1750s, he complained in letters to friends of feeling overworked and overwhelmed. Burnout, it turns out, isn’t a modern condition.
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Linnaeus’s predicament wasn’t new, either. In her book Too Much to Know: Managing Scholarly Information before the Modern Age, the historian Ann Blair explains that since the Renaissance, “the discovery of new worlds, the recovery of ancient texts, and the proliferation of printed books” unleashed an avalanche of information. The rise of far-flung networks of correspondents only added to this circulation of knowledge. Summarizing, sorting, and searching new material wasn’t easy, especially given the available tools and technologies. Printed books needed buyers. And while notebooks kept information in one place, finding a detail buried inside one was another story. Finishing an academic dissertation wasn’t just a test of erudition or persistence; dealing with the material itself—recording, searching, retrieving it—was a logistical nightmare.
Many scholars, like the 17th-century chemist Robert Boyle, preferred to work on loose sheets of paper that could be collated, rearranged, and reshuffled, says Blair. But others came up with novel solutions. Thomas Harrison, a 17th-century English inventor, devised the “ark of studies,” a small cabinet that allowed scholars to excerpt books and file their notes in a specific order. Readers would attach pieces of paper to metal hooks labeled by subject heading. Gottfried Wilhelm Leibniz, the German polymath and coinventor of calculus (with Isaac Newton), relied on Harrison’s cumbersome contraption in at least some of his research.
Linnaeus experimented with a few filing systems. In 1752, while cataloging Queen Ludovica Ulrica’s collection of butterflies with his disciple Daniel Solander, he prepared small, uniform sheets of paper for the first time. “That cataloging experience was possibly where the idea for using slips came from,” Charmantier explained to me. Solander took this method with him to England, where he cataloged the Sloane Collection of the British Museum and then Joseph Banks’s collections, using similar slips, Charmantier said. This became the cataloging system of a national collection.
Linnaeus may have drawn inspiration from playing cards. Until the mid-19th century, the backs of playing cards were left blank by manufacturers, offering “a practical writing surface,” where scholars scribbled notes, says Blair. Playing cards “were frequently used as lottery tickets, marriage and death announcements, notepads, or business cards,” explains Markus Krajewski, the author of Paper Machines: About Cards and Catalogs. In 1791, France’s revolutionary government issued the world’s first national cataloging code, calling for playing cards to be used for bibliographical records. And according to Charmantier and Müller-Wille, playing cards were found under the floorboards of the Uppsala home Linnaeus shared with his wife Sara Lisa.
In 1780, two years after Linnaeus’s death, Vienna’s Court Library introduced a card catalog, the first of its kind. Describing all the books on the library’s shelves in one ordered system, it relied on a simple, flexible tool: paper slips. Around the same time that the library catalog appeared, says Krajewski, Europeans adopted banknotes as a universal medium of exchange. He believes this wasn’t a historical coincidence. Banknotes, like bibliographical slips of paper and the books they referred to, were material, representational, and mobile. Perhaps Linnaeus took the same mental leap from “free-floating banknotes” to “little paper slips” (or vice versa). Sweden’s great botanist was also a participant in an emerging capitalist economy.
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Linnaeus never grasped the full potential of his paper technology. Born of necessity, his paper slips were “idiosyncratic,” say Charmantier and Müller-Wille. “There is no sign he ever tried to rationalize or advertise the new practice.” Like his taxonomical system, paper slips were both an idea and a method, designed to bring order to the chaos of the world.
The passion for classification, a hallmark of the Enlightenment, also had a dark side. From nature’s variety came an abiding preoccupation with the differences between people. As soon as anthropologists applied Linnaeus’s taxonomical system to humans, the category of race, together with the ideology of racism, was born.
It’s fitting, then, that the index card would have a checkered history. To take one example, the FBI’s J. Edgar Hoover used skills he burnished as a cataloger at the Library of Congress to assemble his notorious “Editorial Card Index.” By 1920, he had cataloged 200,000 subversive individuals and organizations in detailed, cross-referenced entries. Nazi ideologues compiled a deadlier index-card database to classify 500,000 Jewish Germans according to racial and genetic background. Other regimes have employed similar methods, relying on the index card’s simplicity and versatility to catalog enemies real and imagined.
The act of organizing information—even notes about plants—is never neutral or objective. Anyone who has used index cards to plan a project, plot a story, or study for an exam knows that hierarchies are inevitable. Forty years ago, Michel Foucault observed in a footnote that, curiously, historians had neglected the invention of the index card. The book was Discipline and Punish, which explores the relationship between knowledge and power. The index card was a turning point, Foucault believed, in the relationship between power and technology. Like the categories they cataloged, Linnaeus’s paper slips belong to the history of politics as much as the history of science.