It's best to start this piece off with a snippet from David Foster Wallace's interview with Charlie Rose (1997) on teaching:
"Don't get me started on teaching. The cliche is true—teachers learn an enormous amount for about 2-3 years but then the curve falls off sharply after. Most of the older teachers that I know, with the exception of a very few geniuses, are extremely bored with teaching and are not very interested in their students. The teachers are going through the motions, the students are going through the motions. The more time and energy spent on teaching, which is extraordinarily hard to do well, the less time you get to spend on your own work. This is my fourth year teaching, and I find myself saying the same things this year as last year—it's a little horrifying."
While the psychological reason (if you want any chance in hell of mitigating the psychological reason, exercise and diet better be priorities for you) has merit, I think the sociological reason is more significant . And I favor the more difficult path after reaching the summit: descend and start again.
Here are the best parts of T. Greer’s piece:
"Several months ago someone on twitter asked the following question: which public thinker did you idolize ten or fifteen years ago but have little intellectual respect for today? A surprising number of people responded with "all of them." These tweeters maintained that no one who was a prominent writer and thinker in the aughts has aged well through the 2010s.
The real question to answer is this: why are so many public intellectuals capable of generating insight, originality, or brilliance at the beginning of their careers, but are utterly incapable of fresh thinking a decade later?
Let me offer two hypotheses. One is psychological, the other sociological.
Psychological:
In most fields creative production increases steadily from the 20s to the late 30s and early 40s then gradually declines thereafter, although not to the same low levels that characterized early adulthood. Peak times of creative achievement also vary from field to field. The productivity of scholars in the humanities (for example, that of philosophers or historians) continues well into old age and peaks in the 60s, possibly because creative work in these fields often involves integrating knowledge that has crystallized over the years. By contrast, productivity in the arts (for example, music or drama) peaks in the 30s and 40s and declines steeply thereafter, because artistic creativity depends on a more fluid or innovative kind of thinking. Scientists seem to be intermediate, peaking in their 40s and declining only in their 70s. Even with the same general field, differences in peak times have been noted. For example, poets reach their peak before novelists do, and mathematicians peak before other scientists do.
Still in many fields (including psychology) creative production rises to a peak in the late 30s and early 40s, and both the total number of works and the number of high quality works decline thereafter.
Fluid intelligence begins declining in a person's 30s. This implies that most humans reach their peak analytic power before 40. Crystal intelligence holds out quite a bit longer, usually not declining until a person's 60s or 70s. This is probably why historians reach peak achievement so late: the works that make master historians famous tend towards grand tomes that integrate mountains of figures and facts—a lifetime of knowledge—into one sweeping narrative.
Thus most humans develop their most important and original ideas between their late twenties and early forties. With the teens and twenties spent gaining the intellectual tools and foundational knowledge needed to take on big problems, the sweet spot for original intellectual work is a person's 30s: these are the years in which they have already gained the training necessary to make a real contribution to their chosen field but have not lost enough of their fluid intelligence to slow down creative work. By a person's mid 40s this period is more or less over with. The brain does not shut down creativity altogether once you hit 45, but originality slows down. By then the central ideas and models you use to understand the world are more or less decided. Only rarely will a person who has reached this age add something new to their intellectual toolkit.
Sociological:
Friedman jets from boardroom to newsroom to state welcoming hall. He is a traveler of the gilded paths, a man who experiences the world through taxi windows and guided tours. The Friedman of the 20th century rushed to the scene of war massacres; the Friedman of the 21st hurries to conference panels. What hope does a man living this way have of learning something new about the world?
More importantly: What incentive does he have to live any other way?
The trouble is that just as our historian reaches her full stature as a public name, her well of insight begins to run dry. A true fan of her works might trace elements of their name-making title back to the very first monograph she published as a baby academic. She was able to take all of the ideas and observations from her early years of concentrated study and spin them out over a decade of high-profile book writing. But what happens when the fruits of that study have been spent? What does she have to write about when they have already applied their unique form of insight to the problems of the day?
Nothing at all, really. Historians like this have nothing left to fall back on except the conventional opinions common to their class. So they go about repackaging those, echoing the same hollow shibboleths you could find in the work of any mediocrity.
In each case the intellectual in question is years removed from not just the insights that delivered fame, but the activities that delivered insight.
The tricky thing is that it is hard to go back to the rap and scrabble of real research when you have climbed so high above it. Penguin will pay you a hefty advance for your next two hundred pages of banal boilerplate; they will not pay you for two or three years of archival research on some narrow topic no one cares about. No matter that the process of writing on that narrow topic refills the well, imbuing you with the ideas needed to fill out another two decades of productive writing.
There are practical implications for all this. If you are an intellectual, the sort of person whose work consists of generating and implementing ideas, then understand you are working against time. Figure out the most important intellectual problem you think you can help solve and make sure you spend your thirties doing that. Your fifties and sixties are for teaching, judging, managing, leading, and dispensing with wisdom. Your teens and twenties are for gaining skills and locating the problems that matter to you. Your thirties are for solving them.
Public intellectuals who do not wish to transition in the their forties from the role of thinker to mentor or manager are going to have a harder time of it. Optimizing for long term success means turning away from victory at its most intoxicating. When you have reached the summit, time has come to descend, and start again on a different mountain. There are plenty of examples of this—Francis Fukuyama comes to mind as a contemporary one—but it is the harder path.”
Good comments:
“All the reasons mentioned in your post are probably true, but I think you're missing one additional, simpler, explanation: regression to the mean. Producing original intellectual works requires creativity and analytical powers, but also one's share of luck. I think it is an often underestimated part of the work of an intellectual, explorer of ideas who can find a nugget of gold in his garden, or find only mud travelling across the continents.This regression to the mean, combined with the loss of creativity, stimulation, and incentives, gives, I think, a reasonable explanation to the short shelf-life of public intellectuals.
Perhaps the ones who fade and spend their lives reiterating their perspective are more public than intellectual.”