In 1862, Moses Hess, a German Jewish socialist who had been a close associate of Marx and Engels, published a book called “Rome and Jerusalem.” Little read at the time, it is recognized today as the first statement of modern political Zionism, the first book to argue that “the pious Jew is above all a Jewish patriot.” When Hess wrote, the prospect of restoring the Jews to political existence in Palestine seemed infinitely remote. Yet he took encouragement from the Risorgimento, which in those years was creating a national state out of the fractured principalities of Italy. “On the ruins of Christian Rome there rises the regenerated Italian people,” he observed; why couldn’t the ruins of Jerusalem provide the foundation for a regenerated Jewish people?

By adopting the title of Hess’s famous tract for his fascinating, extremely rich new history, “Rome and Jerusalem” (Alfred A. Knopf, 624 pp., $35), Martin Goodman exposes the great historical irony behind Hess’s comparison. The reason Jerusalem had to emulate Rome, Hess wrote, was that “though the Jews have lived among the nations for almost two thousand years, they cannot, after all, become a mere part of the organic whole.” Yet Rome itself was the reason why Jews were a Diaspora people, without a nation of their own. In the first century of the common era, Judea was a province of the Roman Empire, yet it still enjoyed considerable autonomy, practicing its own religion under its own leaders. The Temple at Jerusalem — built by Solomon, destroyed by the Babylonians, rebuilt under the Persians, and only recently remodeled in magnificent style by Herod the Great — was both its cultic and its political heart.

All that changed in 66 C.E., when a priest named Eleazar, incensed at Roman high-handedness, led a movement to stop offering the customary Temple sacrifices on behalf of the emperor. What happened next is known to us in considerable detail, thanks to the Jewish historian Josephus, who played a leading role in the ensuing Jewish War. When the Roman governor, Gessius Florus, tried to reimpose his authority, Jewish rebels massacred the Roman garrison, killing some 600 soldiers. Against the odds, they even managed to defeat a much larger, heavily armed legion sent down from Syria to restore order. “Hence it came about,” Josephus wrote, “that the war was so long protracted and the Jews drained the cup of irretrievable disaster.”

For the next four years, the Jews enjoyed a precarious independence. The new government issued coins declaring “Freedom of Zion” and “Jerusalem is Holy,” and even promulgated a new calendar that started, French Revolution-style, with the Year One. But Rome did not become an empire by allowing such rebellions to go unpunished. In 70 C.E., Roman armies led by Titus, the son of the newly crowned emperor Vespasian, stormed Jerusalem and burned the Temple to the ground. The political entity known as Judea, which had existed in some form or another since King David a thousand years earlier, was wiped off the map; Jerusalem was almost completely razed, later to be rebuilt as a Roman colony under the name Aelia Capitolina. It would take nearly 1,900 years before Jewish sovereignty was restored, with the founding of the state of Israel. The Temple, of course, has never been rebuilt.

The war between Rome and Jerusalem was thus the most consequential event in Jewish history, largely responsible for turning Judah the nation into Judaism the religion. It also deserves to be called one of the most important events in world history, because of the way it set the stage for the spread of Christianity. By 70 C.E., the divorce between Judaism and Christianity was neither complete nor inevitable. It was the fall of Jerusalem, and the demotion of the Jews to pariah status in the Roman Empire, that spurred the early Christians to separate themselves decisively from the mother faith. “Among the most important reasons for the growth and spread of Christianity,” Mr. Goodman writes, “one must be that after 70 … Christians presented themselves to the world as unconnected to the Jews.” The conversion of Constantine, the Christianization of the Roman Empire, the growth of the Catholic Church — all were indirect consequences of the Jewish War.

It seems natural, given those enormous ramifications, to call the conflict between Rome and Jerusalem the original “clash of civilizations.” Yet while Mr. Goodman invokes Samuel Huntington’s phrase in his subtitle, it is odd of him to do so, since he believes that this clash was far from inevitable. After a brief prologue summarizing the events of 66-70 C.E., Mr. Goodman, an eminent British scholar of both Roman and Jewish history, embarks on his real subject: an encyclopedic comparison of the way Romans and Jews thought and lived. Drawing on every conceivable source from Tacitus to the Mishnah, and teasing ingenious conclusions from the fragmentary archaeological record, Mr. Goodman discusses religion and politics, economics and warfare, family life and the arts. He deals with large questions of metaphysics and ethics — explaining, for instance, why the Romans thought it was perfectly acceptable to kill their children at birth, while they found the Jewish ban on eating pork laughable. Yet he also evokes the textures of daily life, showing how Romans doted on their pets, while Jews considered even cats to be wild animals.

Mr. Goodman’s engrossing double portrait reveals two very different world views, and shows how much our own civilization owes to both Jerusalem and Rome. From the latter, we inherit our concept of the state, our pursuit of technological progress, and our continual quest for pleasure; from the former, our concept of God and history, and our bedrock faith in the sacredness of the individual. Yet despite these differences, Mr. Goodman concludes, there was no essential reason why Rome and Jerusalem could not have lived together peacefully. “It is in fact rather hard to see any reason why Jews should have experienced particular hostility from Romans before the rebellion broke out in 66,” he writes. “Jews might be ridiculous, intriguing, mysterious or contemptible, but they were certainly not dangerous to the safety and prosperity of Rome.”

The clash of civilizations, then, was not fated but contingent — which perhaps makes it even more tragic. The local tensions between Jews and Romans leading up to the rebellion of 66 C.E. were no worse than both sides had experienced, and overcome, in the past. What made this particular revolt so consequential was sheer bad timing. While Judea was in revolt, in 68 C.E., the emperor Nero was overthrown and killed, leading to a yearlong scramble for power among four leading generals. It so happened that one of them, Vespasian, was the man in charge of the Roman forces in Judea. He had, in fact, been appointed to that post by Nero because he was an unthreatening mediocrity — in the words of Suetonius, “one to whom so great power could be entrusted without risk.”

Yet when fortune left Vespasian holding the crown, after Galba, Otho, and Vitellius had killed one another off, he needed a military triumph in order to legitimize his claim to power. “The new emperor chose to base his claim to the purple on his military services to the Roman state through the defeat of the Jews,” Mr. Goodman explains. While Vespasian tended to affairs in Rome, he charged his son Titus with securing the overwhelming victory he required. And so Titus, who could easily have besieged Jerusalem and waited for it to fall, decided instead to storm and raze the city, regardlessofthecost. Thepropaganda value of the victory was enormous: Vespasian immediately issued coins with the legend “Judaea Capta,” and to this day, visitors to Rome can view the Arch of Titus, which depicts conquered Jews bearing away the menorah from the Temple.

From then on, the Flavian dynasty was committed to portraying the Jews as Rome’s implacable enemies. As a result, it became impossible for the Jews to simply rebuild their Temple, as most conquered peoples were allowed to do. Instead, they were driven from Jerusalem and subjected to a special tax — designated, insultingly, for the upkeep of the temple of Jupiter. All the Jews could do to retaliate was to invent vengeful legends about their conquerors: Mr. Goodman quotes a Jewish folk tale according to which God punished Titus by sending a gnat up his nose, where it rattled around in his brain for seven years.

Mr. Goodman’s analysis of the causes of the Jewish War is necessarily speculative: It is impossible, at such a distance and with such meager evidence, to say exactly why Jews or Romans behaved as they did, or whether things might have turned out differently. But he usefully reminds us of the frightening power of chance in human history. If Eleazar had launched his rebellion a few years earlier or later, if Vitellius had prevailed over Vespasian, the Temple might still be standing today — and the history of the Jews, and the world, would be inconceivably different. It takes a book as magnificently learned as “Rome and Jerusalem” to make such alternative destinies come alive.

akirsch@nysun.com