Not so long ago I speculated in a column in The Atlantic that philosophy might be the most practical college major — and I wasn’t joking. I also wasn’t alone: the financier Carl Icahn and Silicon Valley founders Reid Hoffman and Ivan Karp were phil majors. And for all his professed disdain for the value of higher education, Trumper billionaire Peter Thiel openly acknowledges his debt to Stanford literary theorist and philosopher René Girard for the concept of mimetic theory.

Reaching farther back in time, few people think of philosophers as entrepreneurs, yet one of them, the 18th-century Enlightenment thinker Denis Diderot, deserves the title. He is best known for his groundbreaking reference book set, the 28-volume Encyclopédie, which according to Wikipedia (its latest avatar) sold 4,000 sets during its 20-year publication span and earned a profit of two million livres. The MIT library, proud owner of a set, observes that sets cost up to 1,500 livres when published — over five years’ (admittedly dreadful) wages for a typical manual worker of the era. Enlightenment paid.

Rediscovering Diderot

Recently I had firsthand experience with another side of Diderot’s business genius, the effect named after him. His autobiographical fable, “Regrets for my Old Dressing Gown,” related how a friend’s gift of an elegant dressing gown meant to replace a tattered but much-loved garment turned sour. It made one item of furnishing after another look shabby by comparison, forcing him to replace them all at considerable expense. And despite the outlay, he ended up unhappier than he had been:

My old robe was one with the other rags that surrounded me. A straw chair, a wooden table, a rug from Bergamo, a wood plank that held up a few books, a few smoky prints without frames, hung by its corners on that tapestry. Between these prints three or four suspended plasters formed, along with my old robe, the most harmonious indigence.

Anthropology, like philosophy, may be scorned by today’s Masters of the Universe, yet can also prove useful in the right context. It was the Canadian anthropologist Grant McCracken who rediscovered Diderot’s tale in the late-1980s boom years and used it to describe what he called “a spiral of consumption, in which one acquisition leads to many in a seemingly endless cascade to create a harmonious ensemble of goods.

One Thing Leads to Another

The fashion industry got the point long before McCracken, of course. The industry relies on the imperative of accessories to match a person’s outfit. To be “put together,” shoes, neckties, handbags, watches and the like must evoke similar levels of status unless the “Diderot Effect” is deliberately broken for purposes of irony— think of wearing an $18 Casio digital watch with a $3,000 Alexander McQueen suit.

I recently had a Diderot moment of my own. Appalled by reports of the alleged health threats from plastic cutting boards, I searched for a substitute made of wood and found a beautiful end-grain maple specimen. I realized it was high maintenance, but I am on record for my preference for doing things the hard way — strategic inefficiency, you might call it.

Sure enough, I was soon ordering food-grade mineral oil for maintenance. Then I realized that my decades-old butcher block dining table looked hopelessly shabby near the new cutting board. With limited funds left, I decided to refinish the table myself — which required the purchase of an orbital sander. Fortunately, I’ll be able to use some of the mineral oil to seal the table once I have finished. But the value of the many hours I invested in the process certainly put me in Diderot Effect good standing.

Pleading guilty to succumbing to the effect, I found at least a dozen critics of high consumption warning of its dangers in books, magazines and the digital superhighway — all with no apparent impact on consumer behavior. And how could it be otherwise, with a zillion savvy retailers poised to take advantage? Amazon certainly gets it: Once you click “buy,” the site informs you of a galaxy of merchandise that others have been ordering together to complement one’s own choice.

Indeed, entire industries depend on the Diderot Effect. Camera manufacturers, shaken by the rise of high-quality mobile phone photography, keep their noses above water by luring hobbyists into an endless stream of lenses, filters, tripods, cleaning supplies, lighting and cases. Similarly, in the audiophile scene, there are cables, power conditioners, high-density cabinets and premium discrete digital-to-analog converters to buy. For the 1 percent of 1 percent, the ultimate problem that must be solved is less-than-ideal room acoustics. The remedy: a dedicated listening room with a concrete floor.

According to a summary of research compiled by ChatGPT, scholars can’t agree on how close to the facts of Diderot’s life his essay was — or how deeply opposed he was to the beginnings of Diderot Effect consumption in the 18th century. He was, after all, in the business of selling a 28-volume luxury good, making it psychologically difficult to acquire one volume without the other 27. And while many copies of the Encyclopédie still around show evidence that they were actively read, some contemporaries criticized the project as a status symbol meant to adorn private library shelves — as the 129-pound, 32-volume print edition of the Encyclopedia Britannica was for most of the 20th century.

Diderot wrote a prayer that includes a call to God to destroy the masterpieces we idolize and return us to poverty. Of course, we must take any prayer written by Diderot with a grain of salt — he was once imprisoned for four months as punishment for atheist writings. Still, this brings us to the irony of the Diderot Effect as rediscovered and named a few decades ago by McCracken.

Diderot’s appeal to heaven may have been an in-joke, but there is no doubt that he saw the potential for consumption cascades going too far. And he probably would have been dismayed by the growing applications of his concept in marketing circles over the past three decades.

The website of at least one digital marketing firm, Cyberclick, recently called attention to how widely the concept had become part of 21st-century consumer psychology, known under the trendy jargon “neuromarketing.” The idea is now so popular that the author felt compelled to remind readers that cross-selling (suggesting complementary purchases) and upselling (suggesting more expensive alternatives) should be limited to “genuinely useful” pitches, tacitly acknowledging that the line is often crossed.

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The conservative philosopher Richard M. Weaver called his 1948 critique of Western thought Ideas Have Consequences. I would second that, but — as so often in intellectual history — interpose the word “unintended.”