When Letters Met Algorithms: The Birth of Digital Humanities

In the autumn of 1946, a young Jesuit priest named Roberto Busa stood before the towering headquarters of International Business Machines Corporation in New York City. The building, with its imposing Art Deco façade and the famous globe rotating in its lobby, represented something that seemed utterly foreign to the dusty manuscripts and medieval libraries where Busa had spent his academic life. Yet there he was, clutching a proposal that would seem impossible to most of his colleagues in the humanities: he wanted to use a machine—the IBM 601 punch card sorter—to read and analyze every word that Thomas Aquinas had ever written.

The encounter that followed between Busa and Thomas J. Watson, the legendary founder and president of IBM, would mark one of the most consequential moments in the history of scholarship. It would give birth to what we now call Digital Humanities, establishing a partnership between letters and algorithms that continues to reshape how we study, understand, and preserve human culture. But in that autumn moment, neither Busa nor Watson could have foreseen where this collaboration would lead. They knew only that something remarkable might be possible if a medievalist's obsession with the thought of Thomas Aquinas could be joined with the calculating power of the most advanced technology of the age.

To understand why this moment mattered, we must transport ourselves back to a world very different from our own—a world where the idea of "digital humanities" did not exist, where computers filled entire rooms and required teams of technicians to operate them, and where most scholars viewed mechanized calculation as fundamentally incompatible with the interpretive traditions of humanistic inquiry. In this world, Roberto Busa was something of an anomaly: a man whose faith had led him to scholarship, whose scholarship had led him to philosophy, and whose philosophical questions had led him inexorably to a practical problem that seemed to demand a technological solution.

The Making of a Medievalist

Roberto Paolo Busa was born in 1913 in Varese, Italy, a city nestled at the foot of the Alps that had long served as a center of Catholic learning and religious devotion. Like many young men of his generation and background, Busa entered the Society of Jesus—the Jesuits—at the age of sixteen, beginning the rigorous formation that would shape both his intellectual life and his spiritual practice. The Jesuits had a long tradition of combining deep humanistic learning with scientific rigor, and Busa absorbed this tradition fully during his years of study in Italy and later in Belgium, where he pursued graduate work in philosophy and theology.

It was during this period that Busa encountered the writings of Thomas Aquinas, the great Dominican friar whose theological and philosophical works had shaped Catholic thought for seven centuries. Aquinas represented something unique in the history of Western philosophy: a thinker who had attempted to synthesize Christian revelation with the rational traditions of ancient Greece, creating a comprehensive system that addressed everything from the existence of God to the nature of the soul, from the principles of ethics to the foundations of political authority. For Busa, as for many Jesuit scholars, Aquinas was not merely a historical figure to be studied but a living intellectual companion whose arguments continued to speak to fundamental questions about human existence.

Yet studying Aquinas in the traditional way presented formidable challenges. The collected works of Thomas Aquinas—known in Latin as the *Opera Omnia*—comprise millions of words spanning theological treatises, commentaries on Aristotle, questions and responses on disputed matters, and hundreds of sermons. The sheer volume of material made it difficult for scholars to grasp the full scope of Aquinas's thought or to trace how particular concepts and terms evolved across his career. Worse, the standard tools for navigating this vast corpus—traditional indices, concordances, and specialized studies—were themselves incomplete, inconsistent, and often unreliable. A scholar wishing to understand how Aquinas used a particular term or developed a specific argument might spend months or years chasing down references in scattered secondary sources, never quite confident that they had found everything relevant.

Busa became convinced that there had to be a better way. His training in scholastic philosophy had given him an appreciation for the precision that careful terminology could bring to complex arguments, and he began to dream of creating a comprehensive index—a complete concordance—that would allow scholars to find every occurrence of every word in Aquinas's corpus. Such an index would not merely list words in alphabetical order; it would show each word in its context, allowing readers to understand how Aquinas's meaning shifted and developed as he addressed different questions in different works. This would be, in essence, a map of Thomas Aquinas's intellectual world, rendered in a form that any scholar could consult.

The problem was that creating such an index by hand would take decades, perhaps longer. Aquinas's works comprised an estimated ten million words of Latin prose. Even assuming that a team of trained scholars could process several hundred words per hour—a generous estimate for careful, accurate work—the project would require thousands of person-hours of labor. And this calculation assumed only a simple word listing; a truly useful concordance would need to capture grammatical forms, distinguish between different senses of the same word, and cross-reference related terms. By any reasonable estimate, the project was impossible.

Or rather, it was impossible by the methods that had governed scholarly work for centuries. But Busa had begun to suspect that new methods might be emerging—methods that could transform what scholars could accomplish.

The World of Punch Cards

To understand how Busa's impossible dream became possible, we must first understand the strange and powerful technology that made it so: the punch card computer. In the 1940s, the electronic computers that would later revolutionize human civilization did not yet exist in practical form. The theoretical foundations of computing had been laid by mathematicians like Alan Turing and logicians like Kurt Gödel, but the actual machines that embodied these ideas were still being invented, clunky, unreliable, and extraordinarily expensive. What did exist—and what had existed since the late nineteenth century—were punch card systems: electromechanical devices that could process large quantities of data by reading patterns of holes punched in cards.

The basic principle was elegant in its simplicity. A standard punch card, typically about seven by three inches, contained eighty columns and twelve rows of possible punch positions. Each column could contain a pattern of holes representing a character—a letter, number, or symbol—according to a standard encoding scheme. To input data into the system, an operator would use a keypunch machine to translate text or numbers into patterns of holes, with each keystroke creating a specific combination of punches in a column. The resulting deck of cards could then be fed into a sorter, which could arrange cards in any desired order based on the patterns of holes; a counter, which could add up numerical values; or a collator, which could merge two sorted decks or extract cards meeting specific criteria.

These machines had been developed initially for business applications—tracking inventory, processing payrolls, maintaining customer records—and by the 1940s, they had become essential infrastructure for large organizations. IBM, under the forceful leadership of Thomas J. Watson, had become the dominant manufacturer of punch card equipment, controlling more than ninety percent of the American market. Watson was a showman and a visionary