Sometimes, in spite of all the thinking and planning and pontificating a professor brings to his class, the student says it best.

So it was last week, when my literary theory class was discussing Muriel Spark’s 1959 novel “Memento Mori.”

“I am familiar with ‘coming-of-age’ stories, but this is the first ‘coming-of-old’ age story I have ever read,” wrote one of my students, and I was jealous that I had not been struck by that same clear insight myself.

“Memento Mori” is a peculiar book, but like many of the great novels that came from the 20th-century Anglo-American Catholic literary renascence, it remains a rewarding and provocative book. And yet it is really quite simple. As my student now knows, most of us are indeed going to get old. And as the novel makes clear, all of us are going to die.

In Nicolas Poussin’s 17th-century painting, “Et in Arcadia ego,” a group of innocent shepherds, living the “supposedly eternal life in the pastoral paradise of Arcadia,” examine a monument. The inscription means, “Even in Arcadia, I—death—am there.

We live of course in the age of one of the most irritating and maligned occupations ever conceived: the telemarketer. Yet imagine instead of a solicitation, a poll or a scheme, an exchange as simple as this:

“The telephone rang. She lifted the receiver. As she had feared the man spoke before she could say a word. When he had spoken the familiar sentence she said, ‘Who is that speaking, who is it?’ But the voice, as on eight previous occasions, had rung off.”

And what does the anonymous voice say? “Remember you must die.”

This is the device that drives the plot of “Memento Mori.” Several aging people, all of whom live in London, are the recipients of a series of mysterious phone calls in which a voice eerily reminds them that they are all destined to die. Most of the time the voice is that of a man. Sometimes, it is a woman. Sometimes the voice sounds old, other times young. For one listener it is a quiet, gentle voice. For another, it might be stern. It can be ominous. It can also sound comforting. But always, the message is the same: “Remember you must die.”

Spark opens the novel with three epigraphs: Yeats’s musing on the absurdity of aging, Traherne’s description of the elderly, and The Penny Catechism’s statement that the four last things to be ever remembered are Death, Judgment, Hell and Heaven.

Spark could add two more quotes, I think, that summarize exactly what the novel is about. One would be “Media vita in morte sumus,” or, “In the midst of life we are in death.” A second would be Sigmund Freud’s conclusion that “If you want to endure life, prepare for death.”

Indeed, as one of the characters in the novel says, “You might, perhaps, try to remember you must die. It’s difficult for people of advanced years to start remembering they must die. It is best to form the habit when young.”

As Catholics, we profess to do this all the time, but do we really? My five-year-old son prays nightly that his guardian angel be ever at his side, that the Virgin Mary will pray for him at the hour of his death, that if he should die in the night the Lord will take his soul. How many of us grew up the same way? Just this morning, we had news of a friend’s dying father, and the request for prayer immediately bodied forth the memory of prayers to St. Raphael, St. Joseph, and Thomas Merton’s “Thoughts in Solitude.” They were duly offered up. And yet, to quote Robert Frost, as “we were not the ones dead, we turned to our affairs.”

The same character who urges that we always remember our mortality, especially when young, is a woman living out the last of her years in a nursing home. She reflects further of aging that “It is like wartime. Being over seventy is like being engaged in a war. All our friends are going or gone and we survive amongst the dead and the dying as on a battlefield.”

Now, Spark wrote this dialogue more than 50 years ago. Much has changed. Medicine has advanced; access to humane and dignified care has improved. I know many people over 70, and I would not characterize a single one of them as “old.” In fact, many of them seem as young to me as people my own age. Their age is, in short, irrelevant.

Just as important, the culture has changed. Ours is an age that more than any other seems to believe in immortality. We don’t just embrace the development of miracle drugs; we deceive ourselves into believing that the drugs will allow us to live forever, and we take them without altering our lifestyles or habits at all. We don’t just ease the aches and pains; we erase them and see ourselves as invincible. And if the lines and creases of the years start to become too apparent, we inject ourselves and banish the wrinkles.

Yet as we pop our pills and take our injections and apply the balm and ointments that hide the years, we are all of us, really, like the Arcadian shepherds in Nicolas Poussin’s marvelous painting. The canvas depicts a group of shepherds, living a blissful, innocent and supposedly eternal life in the pastoral paradise of Arcadia. They have come upon a monument; one might even call it a tomb. Inscribed on the stone are the words “Et in Arcadia ego,” literally “Even in Arcadia, I—death—am there.” Imagine how the rest of the shepherds’ day goes! Poussin captures their awe and wonder perfectly, as does Spark when she writes, “How nerve-racking it is to be getting old, how much better to be old!”

This attitude toward an acceptance and understanding of aging and death is best expressed by one of the novel’s most memorable characters, the former detective Henry Mortimer. “If I had my life over again,” says Mortimer, “I should form the habit of nightly composing myself to thoughts of death. I would practice, as it were, the remembrance of death. There is no other practice which so intensifies life. Death, when it approaches, ought not to take one by surprise. It should be part of the full expectancy of life. Without an ever-present sense of death life is insipid. You might as well live on the whites of eggs.”

The wonder of Spark’s novel is that it deals with the admittedly somber themes of death and dying in a way that is actually very funny. Spark satirizes middle-class manners. She lampoons nursing home life. She mimics, and pays homage to, British detective fiction. She reveals all the faults and foibles of our often pathetic human behavior, and yet never becomes didactic or judgmental. In just over 200 taut pages, she forces us to reckon with the inevitability of death even as she allows us to scrutinize our life.

The novel was inspired in many ways by Spark’s own conversion to Catholicism in 1953, as well as hospital visits to see old people she had known as a child. Spark wrote that “when I saw them I was impressed by the power and persistence of the human spirit. They were paralyzed or crippled in body, yet were still exerting characteristic influences on those around them and on the world outside. I saw a tragic side to this situation and a comic side as well.”

Perhaps more than any other book Spark wrote, “Memento Mori” reflects her great theme that everyday life is characterized by both a spiritual presence and the workings of our own individual spirit and conscience.

Who is the mysterious caller that delivers the news we all know, but wish to ignore? I won’t spoil the book for you, but I will assure you that “Memento Mori” is one of the masterpieces of modern Catholic fiction.