Lucretius' De rerum natura is both a philosophical exposition and a (literary) hexameter poem. At 1.146–158, he moves from a therapeutic claim—reason, not sunlight, must drive out mental darkness—to the first principle of his physics: nothing is ever generated from nothing. The grammar does not merely carry a pre-existing proof. Futures, embedded questions, and the repeated language of seeing make the reader enact a movement from frightened observation to causal understanding.
The passage below follows the text of Lucretius, De rerum natura 1.146–158, in the conventional modern lineation. It is printed without macrons and retains poetic contractions such as necessest and divum. Teaching forms in the commentary use pedagogical vowel quantities and the guide's vowel u, consonantal v convention.
The complete passage
hunc igitur terrorem animi tenebrasque necessest
non radii solis neque lucida tela diei
discutiant, sed naturae species ratioque.
principium cuius hinc nobis exordia sumet,
nullam rem e nihilo gigni divinitus umquam.
quippe ita formido mortalis continet omnis,
quod multa in terris fieri caeloque tuentur,
quorum operum causas nulla ratione videre
possunt ac fieri divino numine rentur.
quas ob res ubi viderimus nil posse creari
de nihilo, tum quod sequimur iam rectius inde
perspiciemus, et unde queat res quaeque creari
et quo quaeque modo fiant opera sine divum.
Each line is a dactylic hexameter. Yet the argument crosses line endings: necessest waits for discutiant, nullam rem waits for gigni, and unde waits for creari. A reader must therefore follow syntactic dependencies rather than treating every verse as a complete sentence.
Light that cannot remove mental darkness
Hunc igitur terrōrem animī tenebrāsque necesse est nōn radiī sōlis discutiant, sed nātūrae speciēs ratiōque.
Therefore this terror of the mind and its darkness must be scattered not by the sun's rays, but by the view and rational account of nature.
Accusatives hunc terrōrem and tenebrās are the objects of discutiant, “shake apart, disperse.” Genitive animī modifies both: the fear and darkness are mental, not literal. In the source necessest is a (poetic) contraction of necesse est. The following subjunctive discutiant expresses what must happen; Classical prose also uses necesse est ut ... discutiantur or an accusative and infinitive, depending on emphasis.
The paired subjects create an antithesis. radiī sōlis and lūcida tēla diēī, “the bright missiles of daylight,” are rejected by nōn ... neque. speciēs ratiōque are asserted after sed. Here speciēs nātūrae is not merely “nature's appearance”: it is the apprehended view of nature, while ratiō is the reasoned account that connects appearances to causes. Physical light cannot cure conceptual darkness.
Nōn lūx diēī sed ratiō timōrem discutit.
Not daylight but reason dispels fear.
The principle announced as an infinitive
Prīncipium cuius hinc nōbīs exōrdia sūmet: nūllam rem ē nihilō gignī dīvīnitus umquam.
Its first principle will take its beginning for us from this: that no thing is ever divinely generated from nothing.
cuius points back to nātūrae speciēs ratiōque, the investigation just announced. The future sūmet says where the exposition will begin; dative nōbīs marks the people for whom the beginning is made. The accusative-and-infinitive clause nūllam rem ... gignī supplies the content of the principle. There is no finite Latin verb corresponding to English “is” in “the principle is that ...”; the infinitive itself names the proposition.
gignī is present passive infinitive of gignō, “be generated.” ē nihilō marks source. Adverb dīvīnitus means “by divine agency/intervention,” not simply “divinely” in the approving English sense. Positioning umquam at the end makes the denial unrestricted: at no time does a thing arise from nothing through divine power.
Dīcit nūllam rem sine māteriā gignī.
He says that no thing is generated without matter.
That prose teaching sentence makes the dependency explicit with dīcit. Lucretius instead sets the proposition in apposition to prīncipium, producing the compressed authority of a maxim.
Why fear invents divine causes
Quippe ita formīdō mortālīs continet omnīs, quod multa in terrīs fierī caelōque tuentur.
For fear holds all mortals in this way: they observe many things happening on earth and in the sky.
Accusative mortālīs omnīs uses the i-stem accusative plural in -īs. The ending is especially at home in Republican and poetic Latin, but it is not a case form invented for verse; later prose increasingly favors mortālēs omnēs. Verb continet has singular subject formīdō. The quod clause explains the circumstances that allow fear to grip people. Deponent tuentur is active in meaning and governs accusative multa plus infinitive fierī: “they observe many things happen.” English naturally inserts “that,” but Latin uses an accusative-and-infinitive perception construction.
Bare ablative caelō coordinates with in terrīs as a (poetic) location. Neutral prose would normally repeat the preposition: in terrīs atque in caelō.
Mortālēs fulmina in caelō fierī tuentur.
Mortals observe thunderbolts occurring in the sky.
Causās eōrum operum vidēre nōn possunt.
They cannot see the causes of those events.
In the source, relative quōrum depends on operum, and the whole phrase depends on causās: “the causes of which events.” nūllā ratiōne is an ablative of means or manner, “by no method of reasoning.” The problem is not that events are invisible. Their causes are.
Ac fierī dīvīnō nūmine rentur.
And they suppose that these occur by divine power.
Deponent rentur is present indicative and means “they judge/suppose”; the present subjunctive would be reantur. The understood subject accusative of fierī is opera, recovered from the relative clause. dīvīnō nūmine is ablative of means or agency. Lucretius reports the observers' inference as the next step in their actual reasoning, without endorsing its conclusion.
From completed discovery to clearer sight
Quās ob rēs ubi vīderimus nihil posse creārī dē nihilō, tum iam rēctius perspiciēmus.
For these reasons, when we have seen that nothing can be created from nothing, then we shall perceive more correctly.
The source writes quas ob res, wrapping demonstrative and noun around the preposition. This is ordinary (formal) hyperbaton meaning “for these reasons.” ubi vīderimus is future perfect indicative, not perfect subjunctive in this context: first the principle will have been grasped, then the fuller explanation will follow. Future perspiciēmus answers it. English often uses a present in temporal clauses (“when we see”), but Latin marks the prior future discovery explicitly.
nihil is accusative subject of infinitive posse; creārī depends on posse. The visible chain is therefore vīderimus → nihil posse → creārī. Translating straight to “when we understand creation” loses the hierarchy that makes the proof conditional on an established premise.
Ubi prīncipium cognōverimus, causās perspiciēmus.
When we have learned the principle, we shall perceive the causes.
The two questions the argument will answer
Perspiciēmus unde quaeque rēs creārī queat et quō quaeque modō fīant operā sine dīvum.
We shall perceive both from what source each thing can be created and in what way each thing occurs without the gods' intervention.
After perspiciēmus come two indirect questions. Interrogative unde asks source; quō ... modō asks manner. Their verbs queat and fīant are present subjunctives because the questions are embedded. Distributive quaeque means “each”; in the first question it modifies rēs, while in the second it modifies opera.
Source divum is the (poetic) genitive plural of dīvōrum/deōrum and modifies ablative singular operā, “work, intervention.” The words operā sine exhibit poetic anastrophe: sine follows rather than precedes its ablative complement. Neutral prose would say sine operā deōrum. The point is not that gods cease to exist within the poem. Natural processes can be explained without divine manufacture.
Quaerimus unde rēs nāscātur et quō modō crēscat.
We ask from what source a thing arises and in what way it grows.
The passage's discourse structure is now complete: fear sees unexplained events; fear supplies divine agency; rational inquiry first excludes creation from nothing; only then does it investigate materials and mechanisms. The future tenses make the reader a participant in that research program.
Literal and idiomatic translations
Literal: “Therefore this terror of the mind and its darkness must be scattered not by rays of the sun nor by the bright shafts of day, but by the view and account of nature. Its first principle will take its beginning for us from this: that no thing is ever divinely generated from nothing. For fear holds all mortals in this way, because they observe many things happen on earth and in heaven, whose causes they can see by no reasoning, and they suppose them to happen by divine power. For these reasons, when we have seen that nothing can be created from nothing, then from there we shall now perceive more correctly what we pursue: both from what source each thing can be created and in what way each event happens without the gods’ agency.”
Idiomatic: “So neither sunlight nor the bright spears of day can drive fear and darkness from the mind; only a clear, rational vision of nature can. Our inquiry begins from one first principle: nothing is ever brought into being from nothing by divine intervention. Fear grips people because they watch events in earth and sky but cannot discover their causes, so they assume that divine power produces them. Once we have established that nothing comes from nothing, we can investigate more accurately what each thing comes from and how nature works without intervention from the gods.”
Common Mistakes
1. Making sunlight the successful agent.
❌ Radiī sōlis terrōrem animī discutiunt.
Incorrect reading: Lucretius explicitly denies that sunlight dispels this mental terror.
✅ Nātūrae speciēs ratiōque terrōrem animī discutiunt.
A vision and rational account of nature dispel terror of the mind.
2. Treating nullam rem as the object of gigni.
❌ Nihil nūllam rem gignit.
Incorrect analysis: passive gignī has nullam rem as its accusative subject in indirect statement.
✅ Nūllam rem ē nihilō gignī dīcit.
He says that no thing is generated from nothing.
3. Reading viderimus as ordinary past time.
❌ Ubi vīdimus, tum perspiciēbāmus.
Incorrect sequence for Lucretius' forward-looking program: when we saw, then we were perceiving.
✅ Ubi vīderimus, tum perspiciēmus.
When we have seen, then we shall perceive.
4. Making genitive divum the case governed by sine.
❌ Sine dīvum agimus.
Incorrect analysis: divum is genitive and cannot by itself be the complement of sine.
✅ Sine operā deōrum agimus.
We act without the gods' intervention. (neutral prose)
Key Takeaways
Begin with the finite dependencies: necesse est ... discutiant, formīdō continet, mortālēs tuentur, and perspiciēmus. Then unpack their infinitives and indirect questions. Hexameter delays those dependencies so that the reader moves from darkness, through a first principle, into inquiry. A fluent English translation is the result of that parsing, not a substitute for it.
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