On Feb. 1, 12 days after Donald Trump is inaugurated for the second time, a moment of historical interest will arrive. On that day, Trump will have lived exactly one-third of the lifespan of the American republic.

By my calculations, using the website Howlongagogo.com, Trump will be 28,722 days old. And on that same day, the U.S. Constitution will have been in effect for 86,166 days.

Divide the former by the latter and you get a perfect 0.3333.

This convergence highlights in dramatic fashion how young our model of governance is. The entire run of American constitutionalism, dating back to March 1789 when ratification took effect, can be encompassed in three lifespans. It’s a reminder that what we often consider antique is actually a still-young experiment in the viability of self-government.

The halls of the Philadelphia convention in 1787 echoed repeatedly with usable lessons from the Roman republic and ancient Greece. But their use of ancient references also worked as subtle marketing. James Madison and his brethren published the Federalist Papers under the nom de plume “Publius” at least in part to convey ancient gravitas to their arguments in favor of the Constitution. In 1793, an ordinary Jenkins’ Hill in the newly created District of Columbia was suddenly renamed after Capitoline Hill, an effort to somehow invoke eternal Rome. Even the federal city’s architecture leaned to the neoclassical. The founding generation — and many that followed it — tried to literally cement a sense of perpetuity to the enterprise.

My worry now is that Americans may have overlearned those lessons. Today, we have come to assume the permanence of our political institutions. And that assumption creates alarming vulnerabilities in two principal forms.

The first is casual indifference. A political order that appears to many Americans as permanent — for better or worse — seems beyond their personal ability to do damage. To some extent, the freedom to be indifferent is a great virtue of liberal democracies, where citizens can choose to devote their days to the private affairs of home and market, blissfully unmindful of politics.

More worrisome, however, are today’s political adventurers, who pursue partisan or ideological outcomes by using untested innovations in executive authorities, legislative procedures and judicial doctrines, all with the expectation that the foundations of our constitutional order will tolerate these deviances.

They bank on the resilience of our political order to cover their bets if all goes wrong. The nation has withstood wars and major depressions and uprisings, so all will be fine.

Yet anyone engaged in political demolition without regard for the fragility of the enterprise is at risk of taking down a load-bearing wall.

Long before he became the greatest reformer in American history, Abraham Lincoln delivered a major address to the Young Men’s Lyceum in Springfield, Illinois, which he titled, “The perpetuation of our political institutions.”

Lincoln had grown worried that the nation of his youth had changed. He feared the mutual affections of his countrymen, which had once tied them together in common cause, had disappeared, leaving anger and discontent. “Passion has helped us,” Lincoln observed of the founding period, “but can do so no more. It will in future be our enemy.”

In response, Lincoln had counseled reason, “cold, calculating, unimpassioned reason.”

But his ultimate aim, Lincoln said, was to secure “a reverence for the constitution and laws.” That reverence was the predicate for all the changes he later wrought in America.

Perhaps the first step away from the dangers of that passion, and toward the reasoned reverence Lincoln counseled, is a simple recognition that the perpetuation of our political institutions is not assured — and that our constitutional order has been more fragile than we’ve recently been led to understand.