In 1765, the French philosopher Denis Diderot was genuinely poor. He was famous — co-creator of the Encyclopédie, one of the defining intellectual projects of the Enlightenment — but he could not afford his daughter’s dowry. His solution was to sell his personal library to Catherine the Great of Russia for 15,000 livres, a substantial sum.
With the money, Diderot did something most people would recognize: he bought something nice. Specifically, a beautiful scarlet dressing gown.
What happened next is what makes his story worth knowing more than two and a half centuries later.
The Robe That Broke Him
The robe was elegant — far nicer than anything else Diderot owned. And once he wore it, everything else in his study suddenly looked wrong by comparison. His old desk was battered and plain. His chair was worn. The rug was faded. The straw writing table he had used for years now seemed beneath the quality of the robe.
So he started replacing things. A Damascus rug replaced the old one. A leather armchair replaced the wooden one. Expensive prints replaced the bare walls. A fine writing desk replaced the straw table.
By the time he was done, Diderot owned a perfectly coordinated, luxurious study. He was also broke again.
He wrote about the experience in an essay titled “Regrets on Parting with My Old Dressing Gown” (1769), and in it he captured what had happened with unusual precision: he had been master of the old robe, he wrote, but had become slave to the new one.
What Behavioral Economics Made of Diderot’s Problem
Diderot’s essay sat largely as a literary curiosity until 1988, when anthropologist Grant McCracken formalized the phenomenon in an academic paper. McCracken named it the Diderot Effect and defined it as the tendency for one purchase to create dissatisfaction with existing possessions, triggering a cascade of further purchases to restore consistency.
The mechanism McCracken identified was about what he called consumption constellations — the way objects cluster together into coherent identity sets. A new possession disrupts the existing constellation. The dissonance is uncomfortable. The resolution is more consumption.
This connects directly to research in behavioral psychology that preceded and followed McCracken’s work:
Cognitive dissonance (Leon Festinger, 1957) describes the discomfort people experience when their beliefs or circumstances are inconsistent with each other. Diderot’s new robe created a visual inconsistency with his old study, and the dissonance was resolved by purchasing alignment rather than by returning the robe.
The hedonic treadmill (Brickman & Campbell, 1971) describes the human tendency to return to a stable baseline of satisfaction regardless of positive or negative life changes. A raise, a luxury purchase, or a windfall produces a temporary increase in happiness. Then the new state becomes the baseline, and the old level of satisfaction requires a new stimulus. The treadmill demands you keep running to stay in place.
Relative deprivation theory predicts that people evaluate their possessions not in absolute terms but relative to a reference group. This is why a middle-class income in a wealthy neighborhood produces more dissatisfaction than the same income in a mixed neighborhood. The reference point matters more than the absolute level.
These three mechanisms together explain why more money frequently does not produce proportionally more financial security — the additional income gets absorbed into a higher baseline of expenditure.
Lifestyle Creep Is the Same Mechanism at Salary Scale
The individual purchase cascade Diderot experienced is replicated at income level in what economists call lifestyle inflation or lifestyle creep.
The pattern is consistent: when income rises, expenditure tends to rise at approximately the same rate, leaving the savings rate roughly unchanged. Research from the U.S. Bureau of Labor Statistics consistently shows that households across income brackets save at remarkably similar rates — suggesting that the problem of spending equaling income is not specific to low earners but is characteristic of how most people respond to increases in available resources.
A 2021 study published in the Journal of Economic Psychology found that approximately 60% of individuals who received unexpected income windfalls — inheritances, bonuses, investment returns — had spent the majority within three years. The consumption was not concentrated in large purchases; it diffused across small upgrades in daily expenditure that individually felt trivial.
The mechanism is the same as Diderot’s robe: each income increase creates a new reference point, older spending levels feel inadequate relative to the new baseline, and consumption adjusts upward to match the new identity.
The practical result is that someone earning three times their starting salary may have no more financial resilience than they had as a fresh graduate — and frequently less, because their fixed costs (rent, car payments, subscriptions) have been locked in at the higher level.
Where This Gets Particularly Acute in 2026
The Diderot Effect has always existed, but several current conditions amplify it:
Social media as a continuous reference group signal. Pre-smartphone, reference group comparison happened in bounded social contexts — your neighborhood, your workplace, your immediate social circle. Instagram, TikTok, and LinkedIn have made reference comparison global and continuous. You are not comparing your possessions to your colleagues; you are comparing them to curated highlights of people worldwide who have been algorithmically selected to show you aspirational content. This expands the reference group dramatically and intensifies the dissatisfaction signal.
Subscription-based consumption has made lifestyle creep harder to detect. A one-time purchase of a luxury item is visible. Monthly subscriptions that accumulate — streaming services, meal kits, premium apps, gym memberships, cloud storage tiers — each feel trivially small but compound into significant fixed costs that are rarely reviewed. Unlike Diderot’s rug and desk, these purchases do not create a visible coherent study that might prompt reflection.
Buy-now-pay-later (BNPL) services have compressed the friction between impulse and acquisition. In Indonesia, services like Akulaku, Kredivo, and GoPay Later have made high-ticket purchases accessible on terms that distribute the cost invisibly across future months. This removes the most natural friction point — the moment of payment — that historically created a pause for deliberation.
Practical Responses That Actually Work
The research on what counteracts these tendencies is reasonably consistent, though none of it is magic.
Automating savings before exposure to income. The most reliable intervention found across studies is removing money from the available pool before spending decisions are made. Automatic transfers to savings or investment accounts on payday — before lifestyle spending can adjust to the full income amount — maintain a savings rate regardless of income changes. This is not new advice, but the evidence base for it is strong.
Calculating total system cost before acquiring anchoring items. Diderot’s mistake was evaluating the robe in isolation rather than as the first element of a system that would need to be replaced. Before making a significant purchase, the question worth asking is: what will this make inadequate? What else will need to change for this to work properly or feel right? A new camera body has a system cost that includes lenses, storage, editing software, and carry bags. A new car may have a system cost that includes insurance tier changes, maintenance at dealerships rather than local mechanics, and parking in appropriate areas. Calculating the full system cost rather than the item cost changes the decision significantly.
Reviewing subscription expenditure quarterly rather than monthly. Monthly reviews are frequent enough to feel like a chore but not frequent enough to reveal the compounding effect of accumulated small costs. Quarterly reviews of all recurring charges tend to surface services that have become habitual rather than genuinely used.
Using absolute savings numbers rather than percentage targets as the primary metric. Percentage-based savings targets automatically scale with income, which means that someone earning twice as much has twice the difficulty achieving the same percentage target as their lifestyle adjusts upward. A fixed absolute savings floor — a specific monthly transfer amount that does not change with income increases — is more resistant to lifestyle creep than a percentage target that rises with every raise.
What Diderot Actually Understood
The essay Diderot wrote is more sophisticated than the financial lesson extracted from it. He was not simply complaining about his poor impulse control. He was observing something about the relationship between objects and identity — that things do not simply sit inertly in our lives but actively demand that their surroundings conform to them.
His insight was that the problem was not the robe. The problem was the identity the robe created and the internal logic that identity imposed on everything around it. Once he had accepted a new image of himself, the old objects became incompatible not because they were objectively worse but because they were inconsistent with who he had decided to become.
That is the mechanism. The robe created a new Diderot, and the new Diderot required a new study. The financial consequences were secondary to the identity consequence.
Which suggests that the most durable protection against the Diderot Effect is not rules about spending behavior — though those help at the margin — but clarity about which identity commitments are actually worth making. The robe was worth buying if Diderot had decided, in advance, that his study was staying as it was and the robe would coexist with it anyway. It was not worth buying if the robe was also buying the decision to become someone who lived in a different kind of study.
That distinction — between a purchase and the identity commitment it carries — is one that most financial advice does not address, and one that Diderot understood better than most financial advisors do.
Sources:
- Grant McCracken, “Culture and Consumption” (1988) — original academic formalization of the Diderot Effect
- Denis Diderot, Regrets on Parting with My Old Dressing Gown (1769)
- Brickman & Campbell, “Hedonic Relativism and Planning the Good Society” (1971)
- Leon Festinger, A Theory of Cognitive Dissonance (1957)
- U.S. Bureau of Labor Statistics, Consumer Expenditure Survey (2023)
- Journal of Economic Psychology, windfall spending patterns (2021)
This article is for informational and educational purposes only. It does not constitute financial advice. If you are making significant financial decisions, consult a qualified financial advisor.
