D’Alembert’s Dream
Three linked dialogues stage real people: Diderot first persuades d’Alembert that matter can feel and think; then d’Alembert, talking in his sleep, is overheard by Julie de Lespinasse and the physician Théophile de Bordeu; finally the doctor and Mademoiselle de Lespinasse draw the moral consequences. Images of a swarm of bees, a spider’s web and a sensitive harpsichord make a materialist theory of life imaginable.
Understanding the text
Written in 1769, when Diderot was reading the physiologists and naturalists of his time, the trilogy alarmed d’Alembert and Julie de Lespinasse, who asked that it be destroyed. Copies survived; one circulated discreetly in the Correspondance littéraire in 1782, but the text was first printed only in 1830, long after its author’s death.
Key points
- 01
Living matter
Life is not added to matter from outside: from the egg to the animal, organization and nutrition are enough to turn inert sensibility into feeling and thought.
- 02
Swarm and web
An organism is like a cluster of bees that becomes a single animal, and the self is the centre of a web of nerves, like a spider feeling every thread.
- 03
Everything passes
Species are not fixed: monsters, hybrids and slow transformations suggest that every form passes and only the whole endures.
Explore the ideas in depth
Matter that dreams
Read D’Alembert’s Dream as a philosophical experiment in which sleep and medicine give voice to a materialist theory of life and thought.
Situating the text
Written in 1769, when Diderot was reading the physiologists and naturalists of his time, the trilogy alarmed d’Alembert and Julie de Lespinasse, who asked that it be destroyed. Copies survived; one circulated discreetly in the Correspondance littéraire in 1782, but the text was first printed only in 1830, long after its author’s death. Three linked dialogues stage real people: Diderot first persuades d’Alembert that matter can feel and think; then d’Alembert, talking in his sleep, is overheard by Julie de Lespinasse and the physician Théophile de Bordeu; finally the doctor and Mademoiselle de Lespinasse draw the moral consequences. Images of a swarm of bees, a spider’s web and a sensitive harpsichord make a materialist theory of life imaginable.
Following the arguments
Living matter : Life is not added to matter from outside: from the egg to the animal, organization and nutrition are enough to turn inert sensibility into feeling and thought. Swarm and web : An organism is like a cluster of bees that becomes a single animal, and the self is the centre of a web of nerves, like a spider feeling every thread. Everything passes : Species are not fixed: monsters, hybrids and slow transformations suggest that every form passes and only the whole endures.
Continuing the reading
Read the opening conversation, where a marble statue is turned into flesh, then the dream itself; notice how sleep, medical talk and comedy let Diderot voice hypotheses he could not publish under his own name. Written in 1769, when Diderot was reading the physiologists and naturalists of his time, the trilogy alarmed d’Alembert and Julie de Lespinasse, who asked that it be destroyed. Copies survived; one circulated discreetly in the Correspondance littéraire in 1782, but the text was first printed only in 1830, long after its author’s death.
Questions to carry into your reading
- How do the images of the swarm and the spider’s web explain the unity of a living being?
- Why does Diderot entrust his boldest hypotheses to a sleeping man and a doctor?
A materialism of sensibility explains life without a soul, but it turns the self into a fragile unity that must be described again and again.
How to read it
Read the opening conversation, where a marble statue is turned into flesh, then the dream itself; notice how sleep, medical talk and comedy let Diderot voice hypotheses he could not publish under his own name.
Editions & sources
Summaries and key points are original editorial interpretations. They accompany reading the work and do not replace an edition of the text. Editorial method →