I am deeply grateful to Joe Biden. By defeating Donald Trump in 2020, he rescued this country from the continuing misrule of a dangerous grifter and serial liar, a man gripped by vindictiveness, lawlessness, and egomania. By contrast, Biden presented himself, correctly, as a decent, experienced, and entirely normal politician. He may even have saved his country. Americans owe him a profound debt of respect and appreciation.

He also has no business running for president at age 80. I say that with considerable feeling, being in my late 60s and knowing that my 70s are not far off. I am as healthy as any late-middle-aged person (admittedly, I cringe at the word old, which tells you something right there) can be. But I know that at this stage, I do not have the energy I had a decade ago. I forget more things, and if my body does not hurt when I wake up in the morning, a little voice in my head asks whether I am dead and do not yet know it.

Sixty-seven, in my view, is the new 66. It is an American conceit that aging can be concealed (botox), prevented (exercise! healthy eating!), or ameliorated (don’t wake Grandpa up from his nap!). That is rubbish. Plenty of studies (all available at the National Institutes of Health website) document the impact of aging on memory, mental acuity, endurance; on the production of cortisol and other hormones; and on the increased chances of dementia. Yes, exceptions exist, and we all know a few. But betting on being the exception strikes me as a gamble against ever-lengthening odds and, as the proverb has it, the triumph of hope over experience.

A lot of the clichés about growing older are, unfortunately, entirely correct. Age comes with fewer filters, less patience for fools (or for mere contradiction), and a great deal more “Listen to me, kid, I was doing this before you were born.” If this sounds a bit like Biden, it should. Particularly in the ego- and adrenaline-saturated business of politics, the chances of maturing into sweet-old-grandfatherdom strike me as minimal. One rarely becomes a senator, much less a president, without an unhealthily large ego, which is why Dianne Feinstein and Chuck Grassley find leaving the stage so hard. And even if one started with a certain level of humility, holding on to it is difficult, which is why those who voluntarily step down (think, for example, of Supreme Court Justice David Souter) deserve our respect.

Clinging to office in old age is selfish, too. In my modest line of work of university-level teaching, the ranks are filling with geriatric incumbents who refuse to get out of the way of younger people coming up. They fool themselves into thinking that they are as good as they always were, even as they deliver lectures from 30-year-old notes or cease to produce cutting-edge work. The academic world has its own senatorial- or presidential-size egos, and the result is a comparable level of narcissistic self-indulgence by staying in the spotlight. Quietly, university presidents fret about this, which is why professors my age get attractive buyout offers and various postretirement perks. And before some of my fellow aging pedagogues begin sending me their latest articles in Science or their Boston Marathon times, I will say again, yes, there are exceptions. But then, don’t all of us fool ourselves about how exceptional we are?

President Biden is 80 years old. If he gets reelected, he will be 86 by the time his term expires. He will have spent, at the end of that time, nearly half a century as a senator, vice president, or president, positions all calculated to inflate one’s self-image. As president he has surrounded himself with former aides and dutiful technocrats—no peers who can look him straight in the eye and say, with the gravitas born of expertise and self-confidence, “Mr. President, I profoundly disagree.” Perhaps this is what he has always done, but it is particularly striking now.

The president works out a lot. So did Ronald Reagan, who was already retired by the time he was Biden’s current age. And alas, Alzheimer’s disease did not particularly care about how much brush Reagan had cleared or how often he rode horses. Who has not known some perfectly healthy person in their 80s, 70s, and even 60s whose health suddenly collapsed? Or worse, who went into a sharp decline?

Unfortunately, Vice President Kamala Harris, who has the résumé but seemingly not the political skills and heft to be a compelling presidential candidate, is a weak backfill. Moreover, if history is any guide, an ailing, declining president does not simply say, “You’re right, Doc, time for me to hand over the reins to the veep.” Rather, as Woodrow Wilson, Franklin D. Roosevelt, and others have done, they delay and deny, aided and abetted by families and close advisers who refuse to accept reality.

Nor is Biden the only alternative to Trump. Harris may not be the right person, but what about any of the talented Democratic governors out there? Or a former mayor, such as Mitch Landrieu of New Orleans? Unfortunately we only get the oddballs, such as Robert F. Kennedy Jr., as alternative candidates because today’s Democrats, like their Republican opponents of yore, now fall in line even though they have not fallen in love.

There is nothing morbid in accepting the fact of aging—indeed, there is something pathetic about those who cannot. Cicero gave excellent guidance in his little book How to Grow Old. “This last act must take place,” he writes, “as surely as the fruits of trees and the earth must someday wither and fall. But a wise person knows this and accepts it with grace. Fighting against nature is as pointless as the battles of the giants against the gods.”

Cicero speaks of the joys of age, of contemplating one’s garden (metaphorical and real), of the company of friends old and young, of leaving behind “so many struggles with lust, ambition, strife, quarreling, and other passions.” And he notes that there is something both desperate and inappropriate about trying to stay at center stage to the bitter end. “An actor does not need to remain on stage throughout a play. It is enough that he appears in the appropriate acts.” Joe Biden had the leading role in a crucial act in the grand story of America, and he played it with grace and honor. It is time for him to take a bow, accept the thanks of a grateful nation, and exit to well-deserved applause.