The first thing Anthony Grafton and Joanna Weinberg reveal about Isaac Casaubon in “I have always loved the Holy Tongue” is that he was the owner of two books now housed in Harvard’s Houghton Library. One is a 1578 edition of the comedies of Plautus, which includes a “massive” scholarly commentary. This, we are told, is just the kind of book Casaubon would be expected to own. The second book, from 1554, is Sefer Hinukh behire Yah: John Calvin’s catechism, translated into Hebrew—“a surprising choice of reading for someone who has always been best known as a Hellenist.” These two artifacts establish at once a character and a line of inquiry: a classicist from a vaguely remembered age of erudition, but with some eccentric interests. Who reads Calvin in Hebrew?

While that question lingers, the camera turns, with this anecdote:

More than a century ago, the Jewish scholar Solomon Schechter happened on a curious note in the Otsar haSefarim (Treasury of Books, 1880) of the Hebrew bibliographer Isaac ben Jacob. Ben Jacob mentioned a profusely annotated copy of the medieval scholar David Kimhi’s grammar Mikhlol (Completeness), which belonged to what was then the British Museum. He attributed the notes to one “Rabbi Yitzchak Kasuban,” with whom even the legendarily erudite Schechter was not acquainted. By consulting Joseph Zedner’s catalogue of the Hebrew books in the British Museum, Schechter cleared up the little mystery: “it was no other than the famous Christian scholar, Isaac Casaubon.”

The reader might imagine a vast room full of books and two learned Jews sorting through it together. A door opens somewhere. A silhouette appears. Schechter and ben Jacob look up, squinting to see who it is. A famous Christian scholar has come to visit us? Why?

After a few more formalities—Casaubon has been called the greatest Greek scholar of his time, we are told, and his name haunts the footnotes of a dozen classical authors, even 400 years after his death—we meet him again, at work on one of the critical commentaries that earned him renown. He is reading a Latin translation of the Characters, a set of caricatures composed “for unknown reasons, at an uncertain date,” by Theophrastus, a student of Aristotle. In a sketch titled “The Boastful Man,” Casaubon pauses at a sentence with one transliterated Greek word in it: “He stands right in the diazeugma and tells foreigners how much money he has invested at sea.” “What is he calling a diazeugma?” Casaubon wonders in his commentary. “It seems to be some kind of gap or transverse beam on a bridge,” reads the befuddled translator’s marginal note, “or a port, or the vestibule of a building.” Casaubon decides the text must be corrupt. Drawing a link to a scholium on The Knights by Aristophanes, he argues that the word must be Deigmati, referring to a place outside Athens where foreign merchants gathered to display their wares.

Thus a simple connection, and a correction, reveals a man and a bit of his world: geography, economy, community. That greedy capitalist, counting his profits too soon, is no longer just an illustration of “boastfulness.” He has a place in history, even if he is a fiction. It’s a miraculous result to get from linking some writing of unknown purpose to a footnote to a comedy and correcting a single word. It reveals an integral link between two types of humanism: textual scholarship and the study of humanity.

Who was Isaac Casaubon? His official titles varied. He began his career as an overtaxed professor of Greek at the college founded by Calvin in Geneva; he worked for some years in the library of Henri IV of France, where he was happy enough until his patron was assassinated; he spent his last years in England, serving James I. For both monarchs he acted as an “expert reader,” or a “discourser,” interpreting ancient authors for the moral improvement and practical benefit of the king. He edited and translated classical texts, and published commentaries on them: for example, The Lives of Eminent Philosophers, by Diogenes Laertius; The Learned Banqueters, by Athenaeus; Strabo’s Geography; and the Historiae Augustae Scriptores, a set of dubious biographies of Roman leaders. He also published an influential treatise on ancient satire and attempted a vast critique of a Catholic history of the early church.

Casaubon’s most famous scholarly deed, his proof that the writings attributed to the fabled ancient Egyptian sage Hermes Trismegistus were a later forgery, “helped to unleash a wave of destructive criticism that would eventually reach the Bible itself.” His doubts about the authenticity of our extant texts of Homer were some 200 years ahead of their time, anticipating and influencing F.A. Wolf’s 1795 Prolegomena to Homer. But these historic insights are just a few pages in a vast body of work that many lay readers might see as trivial. Casaubon had a “widely enquiring mind,” as his hilarious entry in the Oxford Dictionary of National Biography puts it, “which led him to write on subjects as diverse as the various ways of mixing wine with water and the surprisingly numerous ancient names for the noises made by different animals and birds.”

Such broad erudition often baffled more modern intellectuals, from Bacon and Descartes to the leaders of the Enlightenment. Immanuel Kant, mentioning Casaubon’s friend Scaliger by name, referred to “those polyhistorians who carry material for the sciences in their heads that would load a hundred camels with books” but who “do not possess the faculty of judgment suitable for sifting all this knowledge for practical use.” Jean Le Rond d’Alembert, in his Preliminary Discourse, blasted such “rude, often ridiculous, and sometimes barbarous learning.” To the Age of Reason, the age of erudition seemed to lack all taste, order or purpose. The advent of the research university in the nineteenth century made it possible for some scholars, especially in Germany, to appreciate their erudite forebears in their own terms, but Casaubon’s inscrutable ambitions were still the riddle at the heart of the last major book about him in English, the standard biography written by Mark Pattison in 1875.

Pattison saw that Casaubon occupied a unique position in the history of reading, at the crossroads of the Renaissance and the Reformation, the turn to pagan antiquity and the turn to Scripture. For him, Casaubon is a tragic casualty of the conflict between religious faith and scholarly objectivity. His setting is dramatic: a Europe marching grimly from the Renaissance to the carnage of the Thirty Years’ War. Casaubon’s Huguenot parents, we are told, were forced “to fly for their lives from Gascony”; his father “had a narrow escape from being burnt alive.” They went to Geneva, where Casaubon was born in 1559, then returned to a small town in France in 1561, where Casaubon’s father led a congregation—but they were never secure. After the St. Bartholomew’s Day Massacre, according to one account, they had to hide out in a cave, where the 13-year-old Casaubon kept up with his Greek by parsing an oration by Isocrates.

Pattison traces Casaubon’s career in minute detail, from Geneva, to Montpellier, to Paris, and across the Channel to England. Again and again, both the facts and Casaubon’s words portray him as a victim of his time, persecuted by Catholics, mistrusted by more radical Protestants, misused by patrons who could not appreciate his genius. Pattison’s story ends in comic misery. Lured at last, against his better scholarly judgment, into religious controversy, Casaubon squanders his final years on a critique of the Annales ecclesiastici of Cardinal Baronio, a twelve-volume history that traced the modern Roman Catholic Church back to the earliest days of Christianity. Casaubon makes it halfway through Baronio’s first volume, to the year 34, when he dies at the age of 55. The autopsy shows a strange malformation in his bladder, “aggravated by sedentary habits, and inattention to the calls of nature, while the mind of the student was absorbed in study and meditation.” Casaubon’s tragic flaw as a scholar, it seems, was his continence: his stubborn determination to hold it all in. It was almost certainly Pattison’s biography that inspired his friend George Eliot to borrow Casaubon’s name for Reverend Casaubon of Middlemarch, the aged pedant who dies trying to write a “Key to all Mythologies.” Scholars have argued that Eliot based the character partly on Pattison, perhaps sensing how strongly the biographer, a dolorous Oxford don, identified with his subject.

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Starting with its sexy title, Holy Tongue is so thorough a reassessment of Casaubon that it also serves as an introduction to him and his world, even though it focuses only on a sliver of his work, his attempts to study Judaic books and manuscripts. Because Casaubon’s Jewish studies are “intimately, even organically connected” to his classical scholarship, Grafton and Weinberg argue, the question of Casaubon and the Jews becomes one about his vocation as a whole. The focus on Casaubon’s Jewish studies is not just some PC intervention into the goyish fields of Renaissance studies and the history of classical scholarship. It captures just those distinctive aspects of Casaubon’s critical practice that we might otherwise miss: his motives, methods and tastes. It shifts the emphasis from his erudition and determination to his creativity and curiosity. It reveals the deeper coherence of his classical scholarship and his Protestantism, and emphasizes the modernity in both.

Holy Tongue refutes that great origin myth of modernity, in which Bacon and Descartes liberate us from a world of obscure and useless learning. It reminds us how much their work took for granted the achievements of that world. The early modern period was an age of “information overload” during which “scholars of encyclopedic and passionate curiosity fought to master the sludgy mass of old and new texts that the presses flung into studies and libraries across Europe.” Taming this textual flood required the humanists to use marginalia, notebooks and memory; to store, process and retrieve amounts of information that seem superhuman today, often constructing vast “memory theaters” out of nothing more than pen, ink and paper. This work was not only technical but also passionate, as Casaubon’s formal rituals show. He combed his hair and prayed for divine assistance before he began to read, much as Machiavelli would dress up in regal garb before he began to discourse with the ancients.

Treating all of Casaubon’s writing, published and unpublished, as one “as yet undefined project,” Grafton and Weinberg work from the “material text,” including Casaubon’s library, his annotations in his books and his notebooks, presenting the individual and his world almost from scratch. The primary evidence is lively, with pictures of pages from Casaubon’s books showing his enthusiastic marginalia; in some places the scribbling is so thick that he has drawn lines on the page to keep his ideas from running together.

In writing about Casaubon, Grafton and Weinberg are also reflecting on their own critical practice as historians (Grafton is a professor of history at Princeton; Weinberg, a Reader in Jewish Studies at Oxford). Casaubon’s identification of the Boastful Man, for example, is an allegory for their own project, its way of moving from books to the individual, weaving a textual web fine enough to trap a personality. This is only one of many instances when the unstated analogy between the authors of Holy Tongue and their subject works to guide the reader—when a fact about Casaubon or a quotation from him, put forth as evidence for some other point, also serves as a clue to the book in our hands.

Grafton and Weinberg admit that their method is demanding. “I have always loved the Holy Tongue” is dense, and the signposts that show the way are easily missed. There is no preface or introduction. As Marx said of Capital, this book assumes a reader who is willing to learn something new, and therefore to think for herself. Casaubon would have approved, to judge from this complaint in his working copy of Polybius: “One thing we do not like in this author is that he repeats, and sets out, his plans, his goals, and his ends so many times. Why did he bother to do this? Did he think he was going to be read only by Greek soldiers or centurions who smell like goats?” But Holy Tongue is full of wonderful details that help carry the reader along. Casaubon misinterprets a Jewish prayer to be said after going to the bathroom as pertaining to the resurrection of the dead; he wonders at a prayer to be recited by men, “Blessed art thou, O Lord, who did not make me a woman”; he takes an interest in a curious story in a book called the Sefer Hasidim, about a woman who refuses to do her ritual mikvah immersion after her period (therefore, refuses to have sex with her husband) because he is not buying enough books. The anecdote resonates with an entry from Casaubon’s diary, showing that he was “as passionate a book-buyer and as dependent for all practical purposes on his wife as any yeshivah bocher.” “Today I paid the booksellers what I owed,” he writes, “except for Norton, my debt to whom is the largest…. I take no thought for my wife, I take no thought for children. Today I decided that until my wife arrives I will not spend more than a gold sovereign on books—unless something truly rare shows up!”

Holy Tongue is arranged topically rather than chronologically, by theme and in order of complexity. Grafton and Weinberg begin with simple examples of Casaubon looking at Jewish miscellany: grammars and prayerbooks, with passages underlined here and there. We gradually get the lay of his inner landscape, spiritual and scholarly, a sense of his passions as well as his methods, and the range of aesthetic, moral and practical expectations that he brings to his reading. He admires the poetic beauty of the Proverbs and hopes to learn a moral lesson from Job. He believes, for a moment, that mastering Hebrew will make it easy to learn Arabic, opening up a new world of Eastern science. (It doesn’t.) He dabbles with speculative etymologies, but he is not so impressed by cabalism as many of his fellow Christians. While trying to study Jewish law, he recognizes Moses Maimonides as an authoritative exegete. “I can say of him what Pliny once said of Diodorus Siculus,” Casaubon wrote: “‘He was the first of his people to desist from playing with words.’” This kind of cultural counterpoint especially interests Grafton and Weinberg. (Did that rabbi just quote Horace, or vice versa?) Casaubon’s boldness as a reader of the Bible is revealed in his heart-rending comment on Isaiah: “There the eternal God pleads his case with insignificant mankind, with so much emotion that no greater indication of the divine goodness could be asked for. It is extraordinary that the immortal God deigns to come to court with men and dispute with them, as if on equal terms. That is the meaning of these words,” quoting here the Hebrew, “‘Come now, let us dispute.’”

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Pattison’s Casaubon has all the trappings of serious scholarship. When it was published, an anonymous reviewer for The Nation was struck by its “minute research,” its “minute truthfulness of statement,” its “careful investigation of minute detail” and its “investigation of minutiae.” Pattison, it seemed, had set new standards for an English-language biography of an early modern scholar, exceeding prevailing norms of both research and realism. He gave “authentic” sketches of Casaubon’s social context: a typically miserable day at a sixteenth-century college, the Machiavellian power struggles among royal librarians. He also used Casaubon’s intimate testimony, drawn from thousands of letters and his remarkable thousand-page diary. Nonetheless, as Grafton wrote in an earlier essay on the book, it “in some ways has as little to do with the historical Casaubon as Middlemarch does.” Because Pattison did not understand the logic connecting Casaubon’s miscellaneous intellectual pursuits, he could imagine them only as a kind of brute mental effort, like preternatural bladder control. Because Casaubon seemed to have no goal other than the unreachable one of infinite learning, he was destined to fail. In the absence of more specific ambitions, everything Casaubon did seemed necessarily a sacrifice, a task imposed on him by his patrons, by the zeitgeist or by his inherent obsessiveness. The great philologist had fallen victim to a devilish form of forgery.

“I have always loved the Holy Tongue” reveals Casaubon’s character, his relationship to his time and to his work on the past, his search for truth and his search for God, with more nuance, depth and coherence than his biography does, in half as many pages. It also restores his personal agency by revealing his sense of purpose and the rewards of his lifelong quest. The contrast with Pattison is particularly stark in the way Holy Tongue ends, with Casaubon’s Faustian final work, the attempted critique of Baronio’s history of the early church.

Rather than seeing it as a torture imposed on him by cruel Anglican overlords, Grafton and Weinberg frame it as an opportunity for Casaubon to apply his hard-won knowledge of Jewish antiquity to a subject dear to his heart. In trying to establish a strict chronology of the Crucifixion by resolving discrepancies in the New Testament (a task that even Casaubon seems to find boring), he is led again beyond the text to human life, and beyond his culture to the Other. He studies how the ancient Jews celebrated Passover and the Sabbath, how they handled necessary tasks when work was forbidden, how they buried their dead. This was, the authors say, “a new approach to the New Testament and to early Christianity.” It is also a moving way to end a book about a scholar who is approaching his own death, showing his broadened sense of the rhythms and cycles of mortal life. The story even has a happy ending. All the while Casaubon has been combing books for knowledge of Judaism, he seems never to have thought to consult an actual Jew. Finally, when working on his Baronio in the Oxford library, Casaubon makes a Jewish friend, Jacob Barnet, who steers him through the thickets of Talmudic commentary and thus contributes in a small way to Casaubon’s last adventure.

In this ending, there is another obvious analogue to the tellers of this tale: one a wide-ranging and eminent historian and essayist, the other a less-famous specialist in Jewish studies, who must have guided her colleague through this foreign terrain. Beyond this, though, the ending seems to offer a picture of something more general, transcending the bounds of discipline and the university. It is one unit of the greater community often called the republic of letters, a community that Casaubon took to be more durable than any church and something distinct from academia. It is telling that Casaubon and Barnet work together in a library, that haven of the independent scholar. Casaubon, who had no formal schooling until he was 19, proudly called himself (in Greek, of course) an autodidact and an ipsomath, a late learner. Leibniz tells a story about him that, if true, suggests that Casaubon was not so impressed by the universities of his time: “The hall of the Sorbonne was shown to Casaubon, and they said to him: this is the place where they have disputed for so many centuries; he replied, to what conclusion have they come?”

The discourser to King James was no humble freelancer. The closest thing to royal patronage today may well be tenure. At a time when we face basic choices about what to do with our universities, libraries and graduate students, Casaubon’s wayward career can help us see better what is at stake in those decisions. It is an example of how the humanities can pursue truth rigorously while still being humane. More than institutions and credentials, canons and curriculums, it shows that the pursuit of humanistic knowledge can be a way of creating new communities. Holy Tongue mentions Middlemarch only in passing, but even those of us who have never made it to the second chapter of the novel may be reminded especially of the sentence that sets it in motion: “The really delightful marriage,” thinks Dorothea Brooke, “must be that where your husband was a sort of father, and could teach you even Hebrew, if you wished it.” Her Reverend Casaubon will make her miserable, but Rabbi Yitzchak Kasuban seems to step forth from that Christian girl’s strange erotic dreams.