Skip to content

The Annotated Edition

171-173:— by Percy Bysshe Shelley

Summary, meaning, line-by-line analysis & FAQ.

This brief poem — comprising three lines of verse and a lengthy French excerpt from Baron d'Holbach's *Système de la Nature* — contends that nothing in the universe occurs by mere chance.

Poet
Percy Bysshe Shelley
The PoemFull text

171-173:—

Percy Bysshe Shelley

No atom of this turbulence fulfils A vague and unnecessitated task, Or acts but as it must and ought to act. ‘Deux examples serviront a nous rendre plus sensible le principe qui vient d’etre pose; nous emprunterons l’un du physique at l’autre du moral. Dans un tourbillon de poussiere qu’eleve un vent impetueux, quelque confus qu’il paraisse a nos yeux; dans la plus affreuse tempete excitee par des vents opposes qui soulevent les flots,—il n’y a pas une seule molecule de poussiere ou d’eau qui soit placee au HASARD, qui n’ait sa cause suffisante pour occuper le lieu ou elle se trouve, et qui n’agisse rigoureusement de la maniere dont ella doit agir. Un geometre qui connaitrait exactement les differentes forces qui agissent dans ces deux cas, at las proprietes des molecules qui sent mues, demontrerait que d’apres des causes donnees, chaque molecule agit precisement comme ella doit agir, et ne peut agir autrement qu’elle ne fait. ‘Dans les convulsions terribles qui agitent quelquefois les societes politiques, et qui produisent souvent le renversement d’un empire, il n’y a pas une seule action, une seule parole, une seule pensee, une seule volonte, une seule passion dans las agens qui concourent a la revolution comme destructeurs ou comme victimes, qui ne soit necessaire, qui n’agissa comme ella doit agir, qui n’opere infailliblemont les effets qu’eile doit operer, suivant la place qu’occupent ces agens dana ce tourbillon moral. Cela paraitrait evident pour une intelligence qui sera en etat de saisir et d’apprecier toutes las actions at reactions des esprits at des corps de ceux qui contribuent a cette revolution.’—“Systeme de la Nature”, volume 1, page 44.

Public domain

Sourced from Project Gutenberg

§01Quick summary

What this poem is about

This brief poem — comprising three lines of verse and a lengthy French excerpt from Baron d'Holbach's *Système de la Nature* — contends that nothing in the universe occurs by mere chance. Every atom, every action we take, and every political shift is linked by a strict chain of cause and effect, enabling a sufficiently astute observer to foresee everything. Shelley draws on d'Holbach's materialist philosophy to support his conviction that the world operates on necessity rather than randomness or divine intervention.

§02Themes

Recurring themes

§03Line by line

Stanza by stanza, with notes

  1. No atom of this turbulence fulfils / A vague and unnecessitated task,

    Editor's note

    Shelley starts with a striking assertion: in what seems like chaos — whether it's a storm, a crowd, or a revolution — every single particle is purposeful in its actions. The term **unnecessitated** carries significant weight; it refers to something "not driven by prior causes." Essentially, Shelley argues that there are no truly free or uncaused events in nature.

  2. Or acts but as it must and ought to act.

    Editor's note

    The final line of the verse tightens the screw. "Must" refers to physical necessity — the laws of nature — while "ought" leans into moral necessity. Shelley blurs the line between how things *are* and how they *should* be, implying that the natural order represents a form of ethics.

  3. 'Deux examples serviront a nous rendre plus sensible le principe…'

    Editor's note

    The French prose passage is taken directly from d'Holbach's 1770 materialist treatise. D'Holbach presents two examples of universal necessity. The first is a whirlwind of dust or a fierce storm: each molecule of water or dust is positioned exactly where previous causes have placed it. A geometer familiar with all the forces involved could demonstrate that each particle could not be found elsewhere or act in any other way.

  4. 'Dans les convulsions terribles qui agitent quelquefois les societes politiques…'

    Editor's note

    D'Holbach's second example moves from physics to politics. In a revolution that brings down an empire, every action, word, thought, passion, and will — from both the destroyer and the victim — plays a crucial role. An intelligence capable of understanding all the interactions between minds and bodies could demonstrate that everyone involved in the upheaval acted as they needed to. Shelley includes this passage because it connects determinism from the natural world to human history, which is the politically charged idea he wants his readers to contemplate.

§04Tone & mood

How this poem feels

The verse lines are calm and assertive — almost mathematical in their confidence. There's no emotional appeal and no lyrical softness. The tone resembles someone who has solved a proof and is just stating the conclusion. The French quotation enhances this with the straightforward, systematic tone of Enlightenment philosophy. Together, they evoke a mood of cool, nearly defiant certainty — the kind of certainty that was truly radical and risky in early 19th-century England.

§05Symbols & metaphors

Symbols & metaphors

Turbulence / the whirlwind
The storm or dust-devil represents all visible chaos—both natural and social. Shelley and d'Holbach illustrate that what seems random to us is, on a causal level, actually well-ordered. It symbolizes the disconnect between human perception and the deeper reality.
The atom / molecule
The smallest unit of matter is the fundamental building block of a deterministic universe. If even atoms follow strict necessity, then nothing at any scale can break free from it. This is where Shelley's materialism begins, at the very foundation.
The geometer
D'Holbach's imagined mathematician, capable of calculating every force and predicting every motion, represents the Enlightenment's vision of pure reason — the belief that a mind, armed with sufficient information, could unravel the entire workings of the universe.
Political revolution
The fall of an empire is the most significant human event d'Holbach can conceive, and he uses this to suggest that history is also driven by necessity. For Shelley, this perspective isn’t pessimistic; rather, it’s empowering: if tyranny comes from necessary causes, then its defeat does too.

§06Historical context

Historical context

Shelley wrote these lines as part of his notes for *Queen Mab* (1813), a lengthy philosophical poem he created when he was just nineteen. He printed it privately to steer clear of legal trouble. The notes are nearly as extensive as the poem and are heavily influenced by French materialist philosophy, particularly d'Holbach's *Système de la Nature* (1770). This work claimed that the universe consists solely of matter in motion, completely governed by natural law, leaving no space for God, free will, or the supernatural. Such ideas were highly controversial in Regency England, where blasphemy and seditious libel could lead to prosecution. Shelley's acceptance of necessity—the idea that every event is the unavoidable result of preceding causes—served as both a philosophical stance and a political tool: if the current social order arises from specific causes, it can be altered by changing those causes. The numbering "171–173" indicates the lines of *Queen Mab* that this note refers to.

§07FAQ

Questions readers ask

Sure! Here’s the humanized version: Not quite, in the usual way. The three lines of verse are a snippet from *Queen Mab*, while the lengthy French excerpt is a prose footnote that Shelley included with them. Combined, they present an argument: the universe operates on determinism, suggesting that everything that occurs is the inevitable outcome of previous causes. Shelley draws on d'Holbach's philosophy to back up this assertion.

Read next

Poems in the same key