The Diderot effect is a social phenomenon related to consumer goods. It is based on two ideas. The first idea is that goods purchased by consumers will align with their sense of identity, and, as a result, will complement one another. The second idea states that the introduction of a new possession that deviates from the consumer's current complementary goods can result in a process of spiraling consumption. The term was coined by anthropologist and scholar of consumption patterns Grant McCracken in 1988, and is named after the French philosopher Denis Diderot (1713–1784), who first described the effect in an essay.
The term has become common in discussions of sustainable consumption and green consumerism, in regard to the process whereby a purchase or gift creates dissatisfaction with existing possessions and environment, provoking a potentially spiraling pattern of consumption with negative environmental, psychological, and social impacts.