Chris Warde-Jones for The New York Times, left; Mark Wilson/Getty Images

David Brooks: Dick, I’m just back from a grueling  five  days during which I took 11 flights — everywhere from Florida to Tucson to Atlanta to Denver to Raleigh ( O.K., I watched Duke crush North Carolina at Raleigh-Durham so that wasn’t so bad).

But I did get to engage in a fair bit of the activity  that others call eavesdropping but I call reporting. I listened to other people’s conversations on the planes, and had a few of my own.

My small sample size confirmed what the polls show — Americans  are in a crappy mood. People on several flights were talking about how rotten Washington is. “They take in a dollar and they spend two,” is how one machinist put it. The only really happy person was a 23-year-old kid I sat next to on a short flight from Atlanta to southern Georgia who had just gotten a job helping to maintain the F-22 for $25 an hour. I didn’t have the heart to ask if the F-22 was being zeroed out in 2010.

But I was hoping to get you to venture a guess about the long-term future of the country. I have always assumed that the U.S. would remain the most powerful and economically important nation in the world for my entire lifetime.

I base that partly in a belief in the permanence of cultural traits. Americans are the hardest working people (or at least the longest working people) on earth. We are really good at disrupting entire industries and starting over (the Europeans are better at steady, gradual change). We have a pretty honest system and we’re an immigrant magnet.

Plus, every previous bout of declinism has been disproved. A few years ago, Arthur Herman wrote a wonderful book called “The Idea of Decline in Western History,” going through the long list of people who have predicted decline — including Herbert Marcuse, Oswald Spengler, T.S. Eliot, William Faulkner and Aleksandr Solzhenitsyn. It’s a great way to sell books, look intelligent and feel superior, but the declinist batting average is .000.

Still, I’m beginning to be infected with the pessimism. A friend who lives in India told me the Indians consider the Chinese their rival for top nation this century. They regard us as already buried. Recent polls have shown that Americans too believe that China will surpass us in global importance.

It’s true I see no way we will avoid a fiscal catastrophe, and I hear smart economists debating how bad the catastrophe will be: Rome or merely Spain? Can this be true? Is the nation of perpetual youth really on the path to old age?

Dick Cavett: What a profound question.  Is this “youthful” country on the way to decrepitude? Many of my friends think it is, as are they.

History is not reassuring on the subject of the longevity of seemingly lasting great nations, is it?

The only person I know who has read every single volume of what Noel Coward, in a lyric, called “Gibbon’s divine ‘Decline and Fall’” is Gore Vidal. You doubtless have. Are there lessons for us there?  I’d love to know how what was ROME became merely Rome, leaving behind some widely scattered aqueducts and old coins. And in my own lifetime we have seen a colossus tumble: the plucky little Soviet Union.

Sometimes I think if I hear the words “health insurance” three more times I’ll have a seizure, requiring mine.   But here’s a nice parallel to your chatting-with-fellow-travelers gleanings:   A friend on business visited five countries in but a few more days.  In each case, aloft and otherwise, she asked, “How’s your health insurance situation in your country? 

The answers, from place to place and not necessarily in this order, were:  “Just fine,”  “Not a problem. Why?” “Takes care of everything.”  “Never have to think about it.”  (Forgive my forgetting one, but it was of a piece.) Their countries aren’t known to be as “great” as ours, but isn’t something amiss here, symptomatic, just possibly, of something decaying at the core?

I suppose our great land still has pockets of the benighted who will see our even speculating on the notion of America’s tumbling from its perch as subversive. I’ve found that — as with surviving admirers of the late tail-gunner, Joseph McC.  of Wisconsin — anything less than nonstop boosterism about the land of the free is considered commie still in some circles.  Maybe we’ll both get the counterpart of my favorite bit of hate mail: a hand-lettered note with return address — on a telegram blank — from Waco, Texas (a favorite choice of dwelling for hate mailers) that ran, “Dear Dick Cavett You Little Sawed-off Faggot Communist Shrimp.”  I wrote back, “I am not sawed off.”  (Do you suppose they got it?  In either sense?)

I guess I like to think that as a people we have a kind of blind knack for pulling back, even if it’s at the last second, from The Abyss. Maybe that and letting fewer highly educated types from Ivy League schools get us into endless, senseless wars; whether they’re MacNamara-type best and brightest or the C-student from Crawford.  Hey, David, you should do a column on that. (I think he did, folks.)

David, I both envy and worry about you.  I get the feeling you are one of those rare beings whose brain is always revving, thinking, analyzing. I have to kick start mine. Unless actively writing or reading good stuff, it’s as if I fall into a sort of fugue state, with the brain in neutral and nothing going on upstairs except maybe the endlessly repeating tune of  the old “Beemans’ Pepsin Chewin’ Gum” commercial from childhood.  Bill Buckley told me that his great (and mine, later) philosophy professor at Yale, Paul Weiss, advised him once to “let the brain rest sometimes, Bill. You don’t need to run it day and night. Like us, it needs a nap.”  Can you, David, switch off that high-powered equipment for a rewarding siesta?

Anyway, D.B., this has been fun.  Please thank the wonderful Gail Collins for relinquishing her role to a fresh-faced, temporary understudy from Nebraska.

Forgot your Groucho snack. Hope it’s new to you. I may have used it in my column.

Groucho Marx was sitting in a restaurant with John Guedel to whom we owe thanks for “You Bet Your Life.”

A couple came over and the man said: Groucho, would you say something insulting to my wife?

Groucho eyed her and delivered: “With a wife like that, you should be able to think of your own insults.”