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In 1485, the Portuguese explorer Diogo Cão erected the Cape Cross monument in what is now Namibia. He and his men had long since passed the boundaries of the space that Europeans had traditionally navigated. They did not and could not know exactly where they were. Still, they were confident that they knew one thing: when they had arrived. They inscribed the cross with a commemorative message, which dated their coming, with a precision that boggles the modern mind, to the year of the world 6685.

To obtain this date they used a method as traditional as their exploits in navigation were radical. The Greek text of the Old Testament, the Septuagint, and most Western world chronicles held that fifty-two hundred years had passed between the Creation and the Incarnation. To locate their particular doings in the longest imaginable term, that of world history, Cão and his men simply added the number of years that had passed since the birth of Christ to this biblical total – which they evidently saw as fixed, governed by an authoritative text, the sort of knowledge that could be set in stone.

In the fifteenth and sixteenth centuries, as everyone knows, European explorers ranged the world and revolutionized – among many other things – the study of geography. They found that the Atlantic and the Indian Ocean, which the world map in the great ancient atlas, Ptolemy’s Geography, represented as closed, really opened to the south. They discovered unknown continents to the west and made contact with a vast range of societies in Africa and Asia as well as the Americas. Gradually even the scholars who stayed home in Europe realized that – as Gerard Mercator put it in 1572 – Ptolemy’s work was now of merely historical interest, and they replaced it with more modern charts.

Explorers and scholars alike understood that their new knowledge of the earth’s surface called many established beliefs into question. When Europeans had known only three continents – Asia, Europe, and Africa – they could easily trace the population of each of them back to one of the three sons of Noah. But from whom did the inhabitants of the Americas descend? Why had the Bible and the ancients not mentioned them? Or did they? Could the newly discovered land of Peru, with its gold mines, be the biblical Ophir that had supplied Solomon with his riches? Was it a Chinese settlement, reached by daring expeditions across the Pacific? Or were the Incas and the other American peoples the children of a separate creation?

The new geography called much in doubt – as the Jesuit José de Acosta famously noticed when he shivered while crossing the equator. Acosta found himself laughing aloud at the Aristotelian doctrine of the torrid zone that was still taught, along with Ptolemy’s more accurate views, in colleges back home in Europe.

Yet most of those who made this revolution in Europe’s mental spaces – explorers like Cão and innovative intellectuals like Mercator – for many years continued to accept a traditional account of historical time. According to this account, history began with the Creation of the world, as narrated in the Bible and pictured in endless sequences of images of the Six Days of God’s work. But this was not the end of the matter, since uncertainty remained about the exact duration of the time between the Creation and the coming of the Messiah. If one accepted the Greek text of the Old Testament as authoritative, the total number of years was fifty-two hundred; on the other hand, if one accepted the Hebrew text of the Old Testament, the biblical total came to around four thousand years. (Thus, in the 1640s, Archbishop James Ussher of England, treating the Hebrew text as authoritative, argued that the world was created in precisely 4004 b.c.)

Whichever version of biblical chronology they accepted, scholars and sailors normally thought that the Old Testament offered a detailed narrative of the early stages of history – especially those that took place before the universal Flood. Where the biblical text thinned out, as it seemed to in the first millennium b.c., the ancient poets and historians chimed in, telling their tales of Troy, Athens, and Rome. These in turn set the stage for the birth of the Savior and the beginnings of a new, Christian age. This age too would end at a determinate time – an eschatological date that radicals set in the immediate future, while more conservative thinkers, who insisted that only God knew when time would have an end, generally placed it within a few hundred years.

While the Western understanding of geography expanded during the Renaissance, then, the traditional dating of the past and future remained curiously narrow-minded. So, at least, one might think, when one stands by Cão’s monument, now in a museum in Berlin – or when one sits in any rare book room and turns the leaves of most of the dozens of chronicles and chronological textbooks produced between 1450 and 1700. These range in size and splendor from Hartmann Schedel’s massive, magnificently illustrated Nuremberg Chronicle of 1493, with its hundreds of woodcuts, some of them the work of the young Dürer, to the Jesuit Denys Petau’s tiny, tight-packed, text-only On the Reckoning of Time, which went through dozens of editions and introduced thousands of schoolboys and scholars to the basic concepts and problems of chronology.

With what now looks like inexplicable patience, the authors of these books built and rebuilt the same basic armature of names and dates. On illuminated scrolls and in heavy printed folios, on wall charts and in textbooks, they packaged history as a single genealogical tree. Rooted in the family dramas of the Old Testament and the Trojan War, the trunk gradually branched out into the ancient Persian, Macedonian, and Roman Empires. Still later, it flowered into the variegated cities and states of the Middle Ages. Again and again, chronologers applied the same techniques to the materials they assembled along the tree’s trunk and branches.

In order to cope with the awkward discrepancy between the Hebrew and Greek texts of the Old Testament, chronologers from the thirteenth century on dated the events of ancient history backward from the birth of Christ, as well as forward from the Creation. By dating backward, chronologers could use both computations, showing how they differed. They assured their readers that they could resolve whatever discrepancies they encountered. Pocket almanacs and wall charts, modest textbooks and stately folios all taught, long before the unfairly notorious Archbishop Ussher came on the scene, that the world began at a particular time on a particular day around 5200 or 4000 B.C., and that scholarly examination of the evidence could securely identify the exact date.

Why all this interest in what Voltaire condemned as “the sterile science of facts and dates, that confines itself to determining the year in which some totally insignificant man was born or died”? We all know that space mattered, in this age of exploration. But time mattered too, in early modern Europe. New devices for measuring the passage of time more exactly than ever before appeared throughout the continent. Immense, spectacular escapement clocks rang the hours in every city square, indicating the phases of the moon and the movements of the planets. Their mechanisms did more than tell time. They mobilized squads of automata, designed to teach moral and theological lessons. Clockwork cocks crowed and clockwork skeletons swung their sickles, all to remind passersby that time moved quickly, so they must hurry to their places of work and worship. Smaller but equally magnificent clocks glittered and rang on every affluent family’s mantelpiece.

Splendid as they were, moreover, these timekeeping devices were only the material embodiment of a new consciousness of time that would, eventually, transform the traditional forms of dating the past. This new consciousness first appeared in the advanced mercantile cities of Italy and Flanders and in the wealthy monasteries of England, France, and the Holy Roman Empire. Old men schooled their sons in the principle that business and politics alike depended on promptness. Long before Protestants appeared on the scene, creating the new ethics of the secular vocation, the Florentine writer Leon Battista Alberti made a character in his dialogues On the Family tell the younger members of his family that “you must always watch the time.” He explained that he kept a diary of engagements, followed it to the letter, and never went to bed with business undone. Clock time drove workers in Europe’s most sophisticated manufacturing enterprises, from Brunelleschi’s workshop to the Venetian arsenal. It also drove the religious to their prayers. Old monks instructed novices just as rigorously as old merchants instructed their apprentices about the vital importance of their daily routine. Monasteries built massive, expensive clocks and bells to teach astronomy and ensure that everyone woke in time to pray. A new sense of time, as something uniform, determined by the stars, and accessible to human industry, pervaded Western culture. It found expression in every imaginable medium: from the paintings that represented Opportunity with the back of her head bald, to the Shakespearian play in which a deposed king cried out, “I wasted time, and now doth time waste me.”

All Europeans, northern and southern, Protestant and Catholic, agreed: societies that measured time accurately were superior to those that did not. The imperial ambassador to Turkey, Ogier Ghislain de Busbecq, mocked his hosts because “they have no chronology,” and thought that Job was King Solomon’s chamberlain, and Alexander the Great the master of his cavalry. By contrast, when Michel de Montaigne read Lopez de Gomara’s account of New Spain, he appreciated the sophisticated calendrics of the Aztecs. The people of the kingdom of Mexico, he concluded, “were clearly more civilized and skillful in the arts” than the other inhabitants of the Americas.

This newfound mania for precision made Christian experts on the calendar rage and mourn, every year, as the Church celebrated Easter on the wrong Sunday. Mother Church was in the wrong. Worse still, in every synagogue in Europe the Jews, who used a more accurate nineteen-year luni-solar cycle, ridiculed the Christians while they themselves celebrated Passover on the correct days. Even a Christian who did not understand the importance of time could hardly claim to be cultured. When an acquaintance asked the mild-mannered Protestant scholar and teacher Philip Melanchthon why he should bother studying chronology, since the peasants on his estate knew when to sow and when to reap without doing so, the Reformer flew into a rage. “That is unworthy of a doctor,” Melanchthon railed: “someone should shit a turd into his doctor’s beret and stick it back on his head.”

If time and the disciplines that opened up its mysteries inspired fear, respect, and fascination, historical time seemed especially alluring. Ancient books – so learned men agreed – contained the keys to the kingdom of knowledge. Only a mastery of historical time could make it possible to set the events they described, the inventions they commemorated, and the philosophical systems they preserved on a single, coherent time line. No wonder, then, that chronology, the scholarly study of time past, attracted ambitious, hard-driving thinkers. Every year at the Frankfurt book fair, the publishers laid out new chronologies for sale. These thick volumes, stuffed with tables and larded with long quotations in Greek and Hebrew, offered their readers long analyses of the dates of world history and the development of every imaginable calendar. Influential scholars wrote them: Luther and Melanchthon, Mercator and Ussher, Newton and Vico.

One chronologer in particular, the Huguenot scholar Joseph Justus Scaliger (1540–1609), won renown for his reformation of the traditional approach to chronology. Working in the decades around 1600, Scaliger relaid the technical foundations of the field.

As Scaliger practiced it, chronology looks startlingly remarkably modern. He treated biblical and classical texts as equally important, and read both with historical insight and imagination. He used dateable eclipses and conjunctions to fix great dates from the fall of Troy to that of Constantinople. And he not only detected gaps in the historical record, but also managed to fill them by astonishing feats of historical detective work. In many cases, the works of ancient historians who offered vital testimony had been lost. Ransacking ancient glossaries and polemical treatises by the fathers of the Church, Scaliger collected and evaluated their fragments. He performed bibliographical and philological miracles, and used their results to create a coherent, solid structure – basically, the one that scholars still use. His achievement inspired widespread excitement. It won him eager, expert readers like Johannes Kepler. It provoked bitter attacks from his Catholic rivals in the Jesuit order. Eventually it gained him a full-time research appointment – the first in modern European history – at the innovative Leiden University.

If time mattered to everyone, chronology mattered to all scholars. In an age of polymaths who mastered all the disciplines, knew many languages, and wrote more than any modern can read, chronology, with its varied contents and technical difficulties, seemed the essence of scholarship. That explains why Scaliger, the most arrogant as well as the most learned of men – he believed he was a descendant of the della Scala of Verona, and wore the purple robes of a prince when carrying out official duties as a professor – chose to cultivate this rocky field.

Formal rhetoric, it has been said, is one of the great obstacles that prevent us from understanding our ancestors. We have forgotten the technical canons that they followed religiously every time they spoke in public, and we fail to see why what now seem empty words once gripped audiences. Technical chronology, in its own way, also stands between us and our scholarly forebears. This densely difficult body of scholarship had, for its sixteenth- and seventeenth-century devotees, something of the all-consuming excitement that structuralism generated in the 1960s. But what they knew as a scene of lively activity, of construction and reconstruction, has become a sunken city. We look up the dates of events in biblical or classical history, the moment at which an eclipse took place or the sequence of Egyptian pharaohs, online or in reference books – and rarely worry how this knowledge was obtained. Experts in chronology – like Bonnie Blackburn and Leofranc Holford-Strevens, the authors of the magnificent Oxford Companion to the Year – still consult Scaliger and his ilk. But they also consult primary sources unknown in the Renaissance, like the masses of dated papyri discovered in Egypt in the nineteenth and twentieth centuries that have transformed our knowledge of how the calendars of Roman Egypt functioned. The waters of oblivion cover the ruined towers of Renaissance chronology.

A few historians have duly celebrated Scaliger’s achievement. A hundred and fifty years ago the brilliant, bitter Jewish classicist Jacob Bernays wrote his biography and hymned his “universal erudition” in phosphorescent terms. So, some years later, did Bernays’s eloquent British friend Mark Pattison – who not coincidentally became the model for George Eliot’s Mr. Casaubon. Yet even Bernays and Pattison, who knew the learned world that Scaliger inhabited at firsthand, did not find it easy to explain what made his work excite his contemporaries so much – much less why an ambitious and brilliant scholar would have chosen the field of chronology as the one in which to exercise his great mental powers. Both of them described chronology, before Scaliger transformed it, as a coherent, unchallenging, elementary discipline – one whose questions and answers were cut and dried, and whose purpose was merely to produce simple tables of the Jewish kings and Roman consuls. “Hitherto,” wrote Pattison, “the utmost extent of chronological skill which historians had possessed or dreamed of had been to arrange past facts in a tabular series as an aid to memory.” He and others have evoked an almost pastoral picture of chronology: herds of contented scholars browse, placidly, over the same stubble of biblical and historical data, constructing baby books for students. Pattison thought that it took a Scaliger – someone whose name had the proverbial power of Einstein’s name, in the mid-twentieth century – to charge it with excitement, to make the pasture a city inhabited by active, irritable crowds.

Early modern readers, however, saw chronology in very different terms. For all its appearance of coherence and simplicity, the field swarmed with challenging, unsolved problems – as becomes apparent when one looks away from the decorative scrolls and wall charts and into the more technical literature of the field. Jean Bodin, a French jurist who brought out in 1566 a pioneering manual on the method for studying history critically, was only one of many Renaissance thinkers who compared chronology to geography. He treated them as twin disciplines: “the two eyes of history,” as he and many others put it. Bodin insisted that no one could practice either of them except by mastering a wide range of disciplines. Like the geographer, the chronologer had to wield not just the philological and hermeneutical keys that could unlock biblical texts and ancient histories, but also the mathematical discipline of astronomy. Only dated astronomical eras and eclipses, in the end, could establish a firm framework for historical time. Yet even astronomical data could not solve every problem. The date of Creation itself, for which scholars had proposed dozens of differing solutions, remained uncertain, as Bodin pointed out. His first readers went through his chapter on chronology pen in hand, eager for enlightenment on what they saw as a difficult and important topic.

When Bodin came to England in the 1580s on a diplomatic mission, the learned Cambridge scholar Gabriel Harvey put him through an interview on chronology. Harvey noted down not a scheme of dates but a bibliography of the best ancient and modern sources for the field – clear evidence that chronology seemed to both men to offer better questions than answers. When Scaliger wrote his first major work in the field, On the Emendation of Chronology, in the early 1580s, he not only made many discoveries and innovations of his own, but also synthesized arguments already made by Bodin and Mercator and by now-forgotten chronologers like Johann Funck and Paulus Crusius. Chronology had already attracted the attention of some of the most innovative thinkers and writers in Europe. Bodin’s Italian Jewish contemporary Azariah de’ Rossi – whose work, in Hebrew, Christian scholars like Scaliger encountered relatively late – labored with equal energy, and quite independently, to reconcile the evidence of the skies with that of the classical and biblical texts, as Joanna Weinberg has shown in her magisterial edition of Azariah’s The Light of the Eyes.

In the middle of the sixteenth century, in other words, informed readers saw chronology not as a fixed textbook discipline but as a challenging interdisciplinary study, one that swarmed with unsolved problems. They had regarded it in the same light a hundred years before, when the brilliant German astronomer Johannes Regiomontanus corresponded with a Ferrarese colleague, Giovanni Bianchini, about the dates of the Savior’s life. And they would find it even more difficult a hundred years after Bodin – when Catholic scholars like Martino Martini and Protestant scholars like Isaac Vossius, who agreed on very little, found common ground in arguing, from the best available historical and astronomical evidence, that Chinese and Egyptian history apparently began before the usual dates for the universal Flood. The textbooks existed. Sailors might think that chronology was simple and uniform. But in the musty libraries where scholars rooted in the past, the study of time seemed just as complex, just as difficult, just as provocative and scary as the study of space.

From the late sixteenth century onward, in fact, religious dissidents regularly cited chronological evidence when they challenged the authority of the Bible. The impious poet Christopher Marlowe, who blasphemed against the Bible in London taverns, had little in common with the pious “Christian without a Church” Isaac La Peyrère, who argued in a scandalous, anonymous book that there had been Men Before Adam. Yet both believed in the deep time of Aztec, Chinese, and Egyptian history, as revealed by modern travelers’ accounts and ancient texts. And both saw it as sufficient reason to reject as absurd the idea that the world could have come into existence a mere fifty-six hundred or sixty-eight hundred years before their own day. Baruch Spinoza seems not to have taken a great deal of interest in chronology. Yet this purportedly mainstream form of scholarship troubled the orthodox and supplied ammunition to Spinoza’s radical allies.

It is not surprising that the study of historical time proved so complex, and even contradictory, in pre-modern Europe. The anthropologist Bernard Cohn showed, in a classic article, that the twentieth-century Indian villagers of Senapur, not far from Benares, found meaning in multiple pasts, ancient and recent, legendary and historical, as their caste memberships and political situations dictated. Learned Europeans, similarly, used chronology to sort out a wide range of problems, from the origins and fate of the universe to the privileges of particular towns, convents, and universities (one of the great chronological controversies of the sixteenth century had to do with the ages of Oxford and Cambridge – a scholarly anticipation of the Boat Race, in which both sides claimed Trojan ancestry). Like the Indians of Senapur, the Europeans of Leiden and London approached the past from many different standpoints. Religious and national, disciplinary and personal attachments shaped their views.

The raw materials that chronologers deployed, moreover, came from an immense variety of sources. Any given scholar attacking a single problem might find himself ransacking the Bible and the Greek and Roman historians, thumbing through modern commentaries on all of these, consulting Islamic astronomical tables, and examining patristic and medieval chronicles – not to mention Renaissance forgeries crafted to show that Pope Alexander VI or the Holy Roman Emperor Maximilian I could trace his ancestry back to the rulers of ancient Egypt. Every library’s reference shelves for history and chronology bent under materials that could explode when combined, and chronology regularly brought these into contact.

Suppose, for example, that a scholar tried, as many did, to fix the exact date of Noah’s Flood. Simple reckoning of the ages at which each of the biblical patriarchs produced his son would not suffice. As we have seen, the Hebrew and Greek texts of the Old Testament differed – in this case by several hundred years. Another source of information had to be found.

Everyone knew that the sun, moon, and planets moved uniformly, that God had set the sun and moon in the skies to rule the seasons and the years. Astronomers could predict their future positions or compute their past ones with certainty. So the scholar might hopefully consult the standard astronomical tables of the time, the Alfonsine Tables, compiled in Christian Spain from Islamic sources. And there he would find what looked like an astronomical date for the Flood. This served as one of the Tables’ epochs, the firm dates from which their authors and readers reckoned later dates and the positions of the planets.

Only one fly disfigured the ointment – but it was a big one, and buzzed loudly. The Alfonsine Tables set the Flood in 3102 B.C. – a date that agreed with neither the Hebrew nor the Greek text of the Bible. Indian astronomers had taken 3102 B.C. as the epoch date of the Kaliyuga, the current celestial cycle. Muslim astronomers took over this usefully early astronomical era, but they also transformed its meaning, as translators so often do. Christian scholars, totally ignorant of Indian astronomy and religion, could not possibly know the date’s origin. Yet some saw the date as the best one they had, since it appeared in an authoritative work on astronomy. As a result, they struggled to explain why the evidence of the book of the heavens departed so radically from Holy Writ.

In this intellectual situation – one in which books theoretically contained all-powerful knowledge, but standard handbooks rested in practice on historically diverse and even contradictory foundations – chronologers naturally came to different conclusions. In fact, they argued so vociferously, over everything from the dates of the kingdoms of Israel and Judah to those of the consuls of ancient Rome, that their quarrels became proverbial. Everyone knew, one seventeenth-century expert wrote to a colleague, that chronologers, like clocks, never agreed.

Scaliger did not invent modern chronology. Rather, he reconfigured the elements of what had long been a fashionable field of study. And his version of it, though powerful and provocative, lasted no more than a generation, since his Jesuit rival, Denys Petau, replaced his work with a more user-friendly, less idiosyncratic synthesis.

To appreciate the explosive impact of this reformation of historical chronology, we need to look backward. For like geography, chronology was an ancient scholarly discipline – one that took shape long before the Renaissance, and that had always drawn methods and materials from widely different traditions.

As early as the fifth century B.C., Greek scholars compiled lists of Olympic victors and priestesses of Hera, to whose years they could affix major historical events. They also tried to use astronomy to date earlier events. A scholar named Damastes noted that according to one text, the moon rose at midnight on the night when the Greeks sacked Troy. He dated the city’s fall, accordingly, to the third quarter of the lunar month in question, when the moon rises late, and this in turn to seventeen days before the summer solstice. His effort and others like it, now obscure and preserved only in scraps of lost texts, were widely known in antiquity. When Virgil wrote in the Aeneid that the Greeks sailed back to Troy “tacitae per amica silentia lunae,” through the friendly silence of the moon, he made clear that he knew exactly when Troy fell. Poets – who in antiquity were often scholars in their own right – studied chronology.

Once Alexander the Great conquered Mesopotamia and Egypt at the end of the fourth century B.C., moreover, new kinds of chronology burgeoned as societies came into close contact for the first time. Scholars from the conquered nations – the Chaldean Berossus and the Egyptian Manetho – drew up chronicles of their kingdoms in Greek, designed to show that their nations and cultures were far older than those of their masters, and thus to avenge their military and political downfall in the realm of the archive. A little later, Greek-speaking Jews did the same.

Meanwhile the Greek scholars who inhabited the new city of Alexandria in Egypt did their best to collate everything they could learn about historical time. Eratosthenes – the Alexandrian scholar now best remembered for his ingenious method of measuring the earth – also drew up chronological tables. These were widely read in a verse reworking by Apollodorus. Already in the ancient world, geography and chronology went together, as demanding technical disciplines designed to put order into the apparent chaos of world history. The rise of empires not only gave rise to a more cosmopolitan view of history, but promoted the technical study of eras and dates.

The Romans of the late Republic and early Empire were as obsessed with time, in their own way, as the Europeans of the sixteenth and seventeenth centuries. Their calendar malfunctioned regularly until Julius Caesar and Augustus reformed it. Their future worried them as well. Throughout the seismic political shifts that brought the Empire into being, prophets and astrologers tried to fix the duration of Rome’s past in order to predict the moment at which the city would fall. The Gauls’ sack of Rome, in which all early records had perished, made the city’s early history obscure. Sorting out the divergent traditions posed endless problems. Some Roman scholars tried to fix their city’s past on massive stone structures, which they inscribed with lists of magistrates and triumphs, year by year. Others, like Varro, who mastered the technical disciplines of Greek scholarship and applied them to the Roman historical tradition, practiced chronology as a technical discipline in the Greek mode. Unable to find historical records that established the date of Rome’s founding beyond doubt, Varro asked an astrologer, Nigidius Figulus, to infer from Romulus’s character the dates of his birth and life. Nigidius did so, using what he thought were the dates of eclipses to gain a fix on Rome’s early past.

In the third and fourth century C.E., finally, Christian scholars set out to fuse all of these materials into a single structure that would encompass Greek Olympic victors, Egyptian pharaohs, and Roman consuls. In late antiquity, both pagans and Christians regularly undertook enterprises like this one, which aimed at the creation of vast taxonomic systems encompassing, in effect, the whole world. As the Oxford classicist Oswyn Murray has pointed out, Ptolemy’s Geography, his astrology, and the later codification of Roman law all represent parallel efforts to impose an intellectual order on the world. But chronology had a special task in addition. It had to show that all of the local histories it encompassed fit a single divine plan, one that led up to the unification of the world by Rome and the appearance of the Messiah. Its internal structure and contents, accordingly, were pulled and torn by contradictions that did not affect the mapping of the earth or the codification of the laws.

Julius Africanus, a third-century scholar based in Rome, did pioneer work. He tried not only to trace the contours of time past, but also to reveal the patterns of time to come, and even to fix the date of the apocalypse. But a slightly later writer, Eusebius of Caesarea, used the materials that Africanus had collected and other sources to establish the basic structures of Christian chronology. Paradoxically, he also laid down the dynamite that would, some centuries later, destroy his creation. Aided by the biblical scholarship of Origen, who had laid out the text of the Old Testament in Hebrew and Greek in parallel columns, Eusebius saw that the Hebrew and Greek texts of the Bible disagreed on chronology. Accordingly, he made no effort to draw up a dated list of events from the Creation. He divided his Chronicle, instead, into two books. In the first he compiled a vast amount of information, some of it quite worrying to a Christian reader – for example, the deep-time chronologies of Egypt and Babylon by Manetho and Berossus. And he frankly admitted that he could not impose order on this troublesome, teeming body of data.

In the second book, by contrast, Eusebius provided something that seems to have been new: a comparative table of world history from the birth of Abraham onward. He laid out dynasties and lists of magistrates in parallel columns that showed when states and dynasties were born, flourished, and died. At times, six or seven nations flanked one another. In the end, however, all of them dwindled down into the single empire of the Romans, which unified the world in time for the appearance of the Savior – and finally, thanks to Eusebius’s patron Constantine, supported Christianity (though Eusebius could not make this point in the early versions of his work, which he completed before Constantine’s victory at the Milvian Bridge). Eusebius, in effect, drew up a highly legible chart of world history, one that adumbrates in its form Charles Minard’s famous diagram of the Napoleonic army’s sufferings in Russia.

Jerome, the biblical scholar who was Augustine’s contemporary, translated Eusebius’s work into Latin. Concerned with practical needs, always worried that too much interest in pagan learning could tempt a Christian scholar to fall away from his true religion, Jerome omitted Eusebius’s troubling first book, and translated only the second, which he also corrected and brought up to date. He thus created what became the chronological tradition in Western Europe: one that taught simple Christian lessons, and used a single, coherent diagram to capture all of world history. It seems natural that later readers and users of Jerome’s work extended it backward to the Creation, as Eusebius had refused to. They were only doing to Jerome what he had done to Eusebius. Latin chronology, accordingly, seemed safe, coherent, simple – except to the few highly perceptive readers who bothered to ask, for example, why Egyptian history, in Jerome’s version of Eusebius, began with the seventeenth, rather than the first, dynasty of pharaohs. The textbooks and wall charts of the Renaissance, like the inscription on Diogo Cão’s cross, derived from Jerome’s work.

In the Greek world, however, scholars continued to read Eusebius’s entire Chronicle. Many found his inclusion of strange material from Egypt and Mesopotamia upsetting. Some – like the Alexandrian scholars Panodorus and Annianus – tried to use astronomical information to impose order on the sprawling mass of Eusebius’s material. Others simply copied it, adding critical remarks. But it was not until the summer of 1602, when Scaliger discovered the remains of Eusebius in Greek, that the explosive potential of his work became clear. Scaliger realized at once that the kingdom of Egypt had begun not only before the Flood, but before the Creation itself. He felt strongly tempted – as he said in marginal notes – to dismiss the new materials Eusebius had collected as obviously false. But he also saw that they were genuinely old and strange. He concluded that they were more likely the work of Egyptian and Mesopotamian scholars who had learned Greek late in life than that of Greek forgers. So he published them, in 1606, to the dismay of many of his Protestant friends and the delight of many of his Catholic critics. Disquieting information had already reached Europe, from both the New World and China. Learned pagan priests, it seemed, claimed that history began long before Europeans thought it had. And now Europe’s greatest scholar had fished up, from an ancient and impeccable source, evidence that posed a radical challenge to biblical chronology.

In other words, Scaliger not only devised what became the modern discipline of chronology; he also opened its ancient Pandora’s box of intractable data about the early history of the world. In geography, knowledge obtained in the great world smashed the walls of the scholars’ hortus conclusus. In chronology, the explosion took place in the garden, when Scaliger dug up and touched off an ancient bomb.

Strong-minded dissenters, as we have seen, seized on all this new information and used it to raise doubts about the inerrancy of the Bible. So, more surprisingly, did highly respectable members of the Jesuit order. In the 1650s, Martino Martini drew up, in Latin, the first history of China based on a wide range of Chinese sources, which he had read in the original. Though Martini hesitated, in the end he argued that recorded Chinese history had begun before the Flood. He felt able to do so, he made clear, because his own teacher, Athanasius Kircher, had shown that the Egyptian kingdom also preceded the Flood. And Kircher, in turn, had learned as much from Scaliger, even though as a good Jesuit he pretended to rely on a different set of sources, one not discovered by a Calvinist. Through the later seventeenth and eighteenth centuries, scholars argued relentlessly about the details of Egyptian and Chinese chronology. Their intricate, sometimes violent debates dragged on for decades, and no solution any of them could propose compelled assent. Edward Gibbon, who avidly read chronology as a boy, recalled in later life that after he steeped himself in that literature, the dynasties of Egypt became his “top and cricket-ball” – toys used in combative play. Eventually, the chronologers’ argument without end brought their whole field – and the authority of the Bible – into widespread disrepute. Giambattista Vico’s New Science represented only one of many efforts to show that all detailed chronologies of ancient times rested on a misconception of the nature of ancient record keeping. Voltaire and other philosophes, less committed than Vico to the tradition of learning, turned chronology into a synonym for sterile pedantry, a noun that almost demanded the adjective ‘mere.’

Chronology, in short, is more than a once-fashionable discipline that has lost its apparent urgency and interest in an age when few professional scholars see the Bible as inerrant and encyclopedias provide all the dates that most of us need. Once upon a time, it was both an ancient and deeply curious tradition and a cutting-edge interdisciplinary field of study. In Europe’s great age of unrestrained, exuberant learning, it attracted the most learned writers of them all. As these giants sorted the rubble of biblical and classical, ancient and medieval, Western and Eastern traditions, they built strange, fascinating new structures from the debris. It’s worth the dive to their sunken city to gain the chance of examining what remains of these.

It seems safe to assume that chronology will never again become fashionable. But the history of this once compelling field is a complex, all too human story that does not quite resemble any other. The ancient geographical system of Ptolemy fell apart when Diogo Cão and others found new lands and seas. The ancient chronological system of Eusebius, by contrast, fell apart when Renaissance scholars did their best to reconstruct it. Sometimes, even scholarship can be renewed from within.