Simone de Beauvoir in 1983. (Photo by Daniel SIMON/Gamma-Rapho via Getty Images)

Old age is the last terra incognita. There are few road maps, and even fewer role models. Sure, there are plenty of old people impersonating young people, but they are role models for old people impersonating young people. They are not role models for growing old.

My role model is Simone de Beauvoir, the French novelist, philosopher and feminist hero. She is an unlikely candidate, I concede. Her writings on old age sometimes make for grim reading. The elderly, she says, are “walking corpses . . . condemned to poverty, decrepitude, wretchedness, and despair.”

Beauvoir’s bleak take on aging was surely influenced by her own circumstances. She wrote those words at age sixty, when her health, until then “embarrassingly excellent,” began to flag. Her step slowed. She was often out of breath. She sneered when anyone mentioned “life’s golden years.” She was determined to write about old age “without glossing it over.”

She did not age gracefully. She aged reluctantly, combatively. She raged, raged against the dying of the light, and against those who denied her this rage, too. Yet in the end she made her peace with old age, came to accept it, and, though she might deny this, came to love it.

Good for her, you say, but do we really need a philosophy of aging? After all, there’s no shortage of scientific research about “successful aging” (such a ridiculous term) or books on diet, exercise, and preventative medicine. What can philosophy contribute to the conversation?

Quite a lot. Philosophy doesn’t teach us what to think but how to think, and we need a new way of thinking about old age. The truth is we don’t really think about growing old. We think about staying young. We don’t have a culture of aging. We have a youth culture to which an aging cohort desperately clings.

Philosophy helps us define our terms. What do we mean by “old”? Chronological age misses the mark. It is meaningless. It tells us nothing about a person, says the contemporary philosopher of aging Jan Baars. “Chronological age is not the cause of anything.”

Old age is not a disease. It is not a pathology. It is not abnormal. It is not a problem. Old age is a continuum, and everyone is on it. We’re all aging all the time. You are aging right now as you read these words — and not any faster or slower than an infant or a grandfather.

As our future shrinks, other futures grow. Our unfinished business will be finished by others. This thought, perhaps more than any other, takes the sting out of old age.

A thought experiment: Imagine a woman growing up on a desert island entirely alone. Does she age? She will develop wrinkles, and inevitably health problems. She will slow down. But is this aging? Beauvoir didn’t think so. For her, aging was cultural, a social verdict rendered by others. If there is no jury, there is no verdict. The girl on the island will experience senescence, biological deterioration, but she will not age.

Beauvoir aged well. She came to terms with her past (“I am satisfied with my fate”), made new friends, and rekindled her love of travel. Old age, Beauvoir believed, should rouse passion, not passivity, and that passion must be directed outward. Have projects, not pastimes. Projects provide meaning. As she says: “There is only one solution if old age is not to be an absurd parody of our former life and that is to go on pursuing ends that give our existence meaning — devotion to individuals, to groups or to causes, social, political, intellectual or creative work.”

Beauvoir was more politically active in her seventies than in her twenties. After decades of hesitancy, she lent her name to many causes. She protested the French wars in Indochina and Algeria, the American one in Vietnam. She intervened on behalf of imprisoned rebels, censored artists, evicted tenants.

She was following a long tradition of elder activism. The 18th-century French philosopher, Voltaire, so bold on the page, only translated that boldness into action late in life. The British philosopher Bertrand Russell, at age eighty-nine, was jailed for seven days for taking part in an antinuclear demonstration. (The magistrate offered to exempt Russell from prison if he promised to behave himself. “No, I won’t,” he replied.)

Benjamin Spock, the renowned American pediatrician, was convicted in 1968 on charges related to his protesting the Vietnam War. He was eighty years old. “At my age, why should I be afraid to make public protests?” he said. This is one of the advantages of old age: you have more to give and less to lose. “A blazing, fearless passion in an old man’s frail body is a moving sight,” says Beauvoir.

And as our future shrinks, other futures grow. Our unfinished business will be finished by others. This thought, perhaps more than any other, takes the sting out of old age. As Beauvoir said: “I love young people and if in their schemes I recognize my own, then I feel that my life will be prolonged after I am in my grave.”

*Portions of this article appear in my book, “The Socrates Express: In Search of Life Lessons from Dead Philosophers.”