For some of the men of America’s founding generation, the world of ancient Greece and Rome was a ready quiver, a source of stories and vocabularies that were of use in the present. Those schooled at Harvard, Princeton, or William and Mary, like John Adams, James Madison and Thomas Jefferson, made their way through tutorials in classical history, often relying on texts in the original languages.

Even for George Washington, whose education took place outside libraries or lecture rooms, figures such as Cicero and Cato were familiar examples of visionary statesmanship or fatal folly.

In colonial America the classics were braided into everyday life. Farmyards might host a horse named Arcturus or a chicken called Cleopatra. For some White households, this conspicuous classicism was put on display in yet another way: in the identities of human beings the families claimed as chattel. Monticello and Mount Vernon flourished only because of the coerced labor of people who had been forcibly recast as Jupiter, Caesar, Hercules and Cupid.

Thomas E. Ricks, a national security journalist and Pulitzer Prize winner, turned to this history out of a sense of bewilderment. Election night in 2016 seemed to call out for a return to first things. He spent the next several years immersed not only in the biographies of the founders but also in their reading lists. His aim was to understand what they perceived to be their cultural heritage and what warnings they might have for the age of Trump: about the pathways of democratic decay, the seductions of tyranny, the wreckage caused by venal politicians, the perils of factionalism.

The result, Ricks’s new book, “First Principles,” is a rich compendium of the ancient wisdom that Washington, Adams, Jefferson and Madison believed they were gleaning from Aristotle or Tacitus, and the formation of “classically shaped behavior” in the early republic. The book is a critical study of the allegories Americans have lived by for more than two centuries, and how they continue to both enlighten and steer us wrong. Ricks charts the dominance of classical allusions in the founding generation and the rapid falloff in the 19th century, as educational systems changed and the demands of practical politics proved less amenable to models derived from Athenians or Romans.

For educated individuals in the late 18th century, a certain image of Greece and Rome was a commonplace of poetry, performance and the built environment. Antiquity mattered, Ricks suggests, because it formed the intellectual foundation for the revolutionary generation. Knowing the source of the values they claimed to espouse and the historical comparisons they took as obvious, we can know more about the founders themselves — and perhaps something of how the country we now have measures up to the one they envisioned.

In addition to wide reading in original texts and the research of specialist historians, Ricks made use of Founders Online, a free database of all the writings of the founding generation, maintained by the U.S. National Archives and Records Administration (and a brilliant example of publicly financed digital humanities). A simple word search reveals precisely how often revolutionary-era figures mentioned “virtue” — a sense of the commonweal or a respect for the public good, as Ricks defines it — as a bedrock principle of civic life. In their writings, the word appears more often than “republic” or “democracy.” Without virtue, institutions failed. Civilization withered. Tyrants reigned.

But “First Principles” is also a reminder that all kinship systems are, in their way, fictive. The founders’ Greece and Rome was not ours. Since the ancient world is likewise so available to us today — Capitol Hill, marathons, the Socratic method and at least 30 American cities named Troy — it takes some effort to realize how bizarre it was for a Virginia planter or a Boston printer to think of himself as an inheritor of this bygone world.

To claim that cultural descent, he had to ignore the millennium when Rome resided not on the Tiber River but on the Bosporus, ruling an increasingly Asian empire from Constantinople. He had to overlook the centuries when Greek texts were preserved and reworked in the great Islamic centers of learning from Cordoba to Baghdad. In an age that was just beginning to define “race” as the basic form of human difference, he had to reimagine Mediterranean and North African civilizations as racially White. And he had to cast his own prejudices — women as fit mainly for domestic life, same-sex love as immoral, hereditary enslavement as part of the natural order — as timeless and universal. This entire process, from the Renaissance to the Enlightenment, was not so much about the resurrection of the ancient world as its transfiguration, a multi-century habit of rendering the ancients comprehensible to Northern Europeans.

“First Principles” closes with some regrets about “the end of American classicism” and a set of practical lessons that, although laudable, seem disconnected from the rest of the book, such as curtailing campaign spending. However, we shouldn’t mourn the passing of a version of America’s cultural heritage that has always been based on rather bad history. Ricks doesn’t rhapsodize about the ancients, but there are plenty of people who do, often in grotesquely ignorant ways. “Our mission is to defend the legacy of America’s founding, the virtue of America’s heroes and the nobility of the American character,” President Trump said on Sept. 17 in announcing the creation of a new 1776 Commission to promote “patriotic education.” He went on to label the U.S. Constitution as “the fulfillment of a thousand years of Western civilization.”

As a field, classics is doing fine without contorting it to serve nationalism. In 2016, the last year for which data is available from the Modern Language Association, college Greek and Latin courses enrolled about 36,000 students, compared with about 50,000 for Chinese — hardly a sign of dead languages. In 2017, according to the American Council of Learned Societies, Latin was in fourth place in the number of K-12 programs, behind Spanish, French and German but ahead of Chinese and American Sign Language.

New scholarship has reinvigorated — and complicated — our understanding of the classical age. Scholars today know Greece better for provincializing it, placing its texts and iconography alongside those of contemporary Persia, India and China. Archaeologists and historians such as Mary Beard have rendered Rome more familiar by making it weirder — fewer togas and speeches, more grime, violence, sex and angst. (Roman virtue, it turns out, was not exactly what the Enlightenment believed it to be.) Translators and critics such as Emily Wilson and Daniel Mendelsohn have remade the great texts from scratch, in the process emphasizing a point that escaped Jefferson and Madison: that the classical world was peopled by women, too.

The dead are not our employees, as the novelist Hilary Mantel once remarked. The classical world is most intelligible when we give up requiring that its inhabitants play walk-on roles in our own narratives. That is why W.E.B. Du Bois could say, in “The Souls of Black Folk,” that it was an act of liberation to “summon Aristotle and Aurelius and what soul I will, and they come all graciously with no scorn nor condescension.” As Ricks’s searching account shows, what feels truly elegiac is to be reminded of a time in American history when political leaders, for all their faults, valued erudition and, yes, a certain brand of virtue as ideal qualities in public life.

First Principles

What America’s Founders Learned From the Greeks and Romans and How That Shaped Our Country

By Thomas E. Ricks

Harper. 386 pp. $29.99