To Tuchman, folly begins with the most fundamental of things: an outsize and self-destructive will to power. Both the governors and the governed can overreach, convinced of their own rectitude and righteousness. “Chief among the forces affecting political folly is lust for power, named by Tacitus as ‘the most flagrant of all the passions,’” Tuchman wrote. “Because it can only be satisfied by power over others, government is its favorite field of exercise,” or what she calls the “paramount area of folly because it is there that men seek power over others — only to lose it over themselves.” In this light, President Trump and his alt-right coterie are not something new under the sun but another chapter in the oldest of human dramas: the tension between appetite and the common good, between ambition and common sense.

There is a lesson here not only for the president but for the people — particularly the people who chose to support him in 2016 and who stand with him now, apparently come what may. “Persistence in error is the problem,” Tuchman wrote. One of the more troubling features of popular political life is blind tribal loyalty — the refusal to acknowledge that your chief or your kind could be wrong. A perennial issue, this reflexive defensiveness is especially pronounced at the moment. But the historically literate voter, like a historically literate decision maker, need not be captive to previously held opinions at all times and at any cost. “There is,” Tuchman wrote, “always freedom of choice to change or desist from a counterproductive course if the policy-maker” — or, in my view, the voter — “has the moral courage to exercise it. He is not a fated creature blown by the whims of Homeric gods. Yet to recognize error, to cut losses, to alter course, is the most repugnant option in government.” And in the mind and heart of a fervent voter who was determined to send a message to Washington that business as usual was not working. The question now, more than a year into business as unusual, is whether those who supported the populist insurgency of 2016 will honestly assess its effectiveness in 2018 and in 2020. “Wooden-headedness” in the Oval Office, alas, begins in the voting booth.

How do we stop marches of folly? Tuchman was thoughtful on the question, realizing that history was not a panacea. “Whole philosophies have evolved over the question whether the human species is predominately good or evil,” she wrote. “I only know that it is mixed, that you cannot separate good from bad, that wisdom, courage and benevolence exist alongside knavery, greed and stupidity; heroism and fortitude alongside vainglory, cruelty and corruption.”

That observation appeared in a 1981 collection of her essays titled “Practicing History.” Perhaps her least known work, it is engaging and wise, and in it she took a proportionate view of the human condition. “Amid a mass of worldwide troubles and a poor record for the 20th century,” Tuchman wrote, “we see our species — with cause — as functioning very badly, as blunderers when not knaves, as violent, ignoble, corrupt, inept, incapable of mastering the forces that threaten us, weakly subject to our worst instincts; in short, decadent.”

It was, she argued, an easy, if unhappy, case to make at the time. (As it is now.) “A century that took shape in the disillusion which followed the enormous effort and hopes of World War I,” Tuchman wrote, “that saw revolution in Russia congeal into the same tyranny it overthrew, saw a supposedly civilized nation revert under the Nazis into organized and unparalleled savagery, saw the craven appeasement by the democracies, is understandably marked by suspicion of human nature.”