Democritus: 'Only Atoms and the Void Truly Exist' — The Philosopher Who Rebuilt the World from Particles

Key Takeaways

• Atoms (atomon) and the Void (kenon): Democritus explained all things by means of indivisible, infinitesimal particles (atomon = atoms) and the void (kenon). Atoms differ only in shape, size, and arrangement; their combination and separation account for the generation and destruction of all things. His revolutionary stroke was to introduce the void — which Parmenides had denied — and thereby provide a rational explanation of change and diversity.
• The subjectivity of sensation and the dual structure of cognition: Sensory qualities such as colour, taste, and temperature exist only "by convention" (nomos); what truly exists is atoms and the void alone. Sensation is called "dark cognition" and reason "genuine cognition" — a distinction that anticipates the modern division between primary and secondary qualities.
• Euthymia (tranquillity of the soul): Democritus did not confine himself to natural philosophy; he carved out a distinctive position in ethics as well. He made the goal of the good life not the maximisation of pleasure but a measured joy — the tranquillity of the soul (euthymia). This thought directly anticipates Epicurus' later ideal of ataraxia (freedom from disturbance).

Life and Historical Context

Democritus was born around 460 BCE in Abdera, a colonial city in Thrace. Abdera was often looked down upon as a provincial town by mainland Greece, but the Sophist Protagoras also came from Abdera, indicating that it was an intellectually vibrant city. According to Diogenes Laërtius (Lives of the Eminent Philosophers IX.34–49), Democritus was born into a wealthy family and spent his father's inheritance travelling widely to various lands.

Tradition relates that Democritus journeyed to Egypt, Persia, and possibly even India (Diogenes Laërtius IX.35). The extent of these travels is probably exaggerated, but it is certain that he possessed wide-ranging knowledge and had been exposed to many intellectual traditions. He himself declared: "I have wandered over more of the earth than any man of my time and made the most extensive investigations" (DK 68B299).

Democritus' teacher was Leucippus. It was Leucippus who first originated atomism, and Democritus who developed it systematically. Aristotle treats the two as virtually interchangeable (On Generation and Corruption I.8, 325a–b), yet Democritus far surpassed his master in extending atomism to epistemology, ethics, and cosmology. Very little is known about Leucippus — Epicurus even doubted his existence (Diogenes Laërtius X.13) — but modern scholarship widely accepts his historicity.

Democritus' literary output was enormous in antiquity. The catalogue drawn up by Thrasyllus lists more than seventy works organised in tetralogies (Diogenes Laërtius IX.46–49), spanning physics, mathematics, ethics, literary criticism, and technical treatises. Cicero praised Democritus' prose style as "clear and beautiful" (De Natura Deorum I.120), and Diogenes Laërtius notes that his writings were considered on a par with Plato's (IX.49). Yet not one of his works has survived intact. All that remains are fragments and testimonies preserved by later authors (DK 68).

The age in which Democritus was active spanned the golden age of Periclean Athens to the upheavals of the Peloponnesian War (431–404 BCE). Socrates was his contemporary, yet Plato's dialogues contain no direct reference to Democritus. Diogenes Laërtius reports the anecdote that Plato wished to burn all of Democritus' writings but was dissuaded by Pythagorean friends (IX.40). Whatever the credibility of this story, a fundamental opposition between materialism and the theory of Forms certainly existed between the two thinkers.

Democritus is said to have been long-lived, dying around 360 BCE at the age of ninety or more (some traditions put him at over a hundred).

Mini-Timeline

• c. 500 BCE: Birth of Leucippus (estimated). Originates atomism
• c. 490 BCE: Period of activity of Empedocles and Anaxagoras
• c. 460 BCE: Democritus is born at Abdera
• c. 450–430 BCE: Studies under Leucippus. Inherits and develops atomism
• c. 440–420 BCE: Travels to Egypt, Persia, and elsewhere (according to tradition)
• 431 BCE: Outbreak of the Peloponnesian War
• c. 420–400 BCE: Composition of his major works (estimated), including Great World-Order and Little World-Order
• 399 BCE: Death of Socrates
• c. 360 BCE: Democritus dies (estimated, aged ninety or more)

What Did This Philosopher Ask?

Parmenides' argument had declared that change, motion, and plurality are logically impossible. Being is one, unmoved, and unchanging. Yet before our very eyes stretches a world that ceaselessly changes and moves. The philosophers after Parmenides grappled with the challenge of bridging this gulf between theory and reality.

Empedocles explained change through the combination and separation of four elements (earth, water, fire, air); Anaxagoras introduced infinitely many seeds (spermata) and Nous (Mind). Democritus' answer was the most radical of all. He asked: what is the smallest unit of being, how do these units produce the diversity of the world, and to what extent can we know reality through the senses?

Democritus' originality lay in squarely accepting Parmenides' logic while nevertheless granting a kind of reality to the void — the "non-Being" that Parmenides had rejected. "What-is is no more real than what-is-not" (reported in Aristotle, Metaphysics I.4, 985b4–10) — this single dictum was a revolutionary reversal that shattered the dualism of Being and non-Being.

Core Theories

1. The Atom (atomon) — That Which Cannot Be Divided

The foundation of atomism is the following thesis. If one continues dividing a body, one will eventually reach a smallest, indivisible unit — the atom (atomon, Greek for "uncuttable"). Atoms are ungenerated, imperishable, and unchanging; they are solid bodies (naston, "the full") containing no internal void.

Why did Democritus think that division cannot continue without limit? According to Aristotle's report (On Generation and Corruption I.2, 316a–317a), if a body were divisible without limit, one would ultimately arrive at "extensionless points." But no number of extensionless points, however large, can constitute a body with extension. Therefore bodies must have a lower limit of division — the atom. This is at once a physical limit of division and a logical necessity.

Atoms are infinite in number and move eternally through infinite void. When atoms collide, those whose shapes interlock combine; those that do not fit bounce apart. What we call "generation" is the combination of atoms; "destruction" is their separation. The atoms themselves never change — all that changes is their arrangement and configuration.

2. The Void (kenon) — The Rehabilitation of Non-Being

Parmenides had dismissed the void — non-Being — as logically impossible. Yet Leucippus and Democritus, arguing that motion cannot be explained without void, granted the void a kind of existence. Aristotle reports their position as follows: "They call the full (to plēres) and the void (to kenon) 'being' and 'non-being' respectively, and say that being is no more real than non-being" (Metaphysics I.4, 985b4–10).

This was a bold ontological move. "What is not" nonetheless "is" — the void contains nothing, yet it exists. As the arena in which atoms move, the void is indispensable and enjoys an ontological status equal to that of atoms. The concept of the vacuum in modern physics — not an empty space but a field — is a distant echo of this ancient intuition.

3. The Differences Among Atoms — Shape, Arrangement, Orientation

Aristotle classifies the differences among atoms under three headings (Metaphysics I.4, 985b13–19). (1) Shape (rhysmos) — as A differs from N. (2) Arrangement (diathigē) — as AN differs from NA. (3) Orientation (tropē) — as N, when rotated, becomes Z.

This analogy is noteworthy. Just as a small number of letters of the alphabet can produce an infinity of sentences, so the combinations of a limited set of atomic shapes, arrangements, and orientations generate the diversity of all things. Atoms possess neither colour, nor taste, nor temperature. These qualities arise only when aggregates of atoms act upon our sense organs — they are merely subjective experiences.

The size of atoms also deserves attention. Atoms are normally too small to be seen, but some testimonies suggest that Democritus set no upper limit on their size (Diogenes Laërtius IX.44; Aëtius I.12.6). Moreover, whether atoms possess weight (baros) is a matter of scholarly debate. Aristotle attributes weight to atoms (On Generation and Corruption I.8, 326a9–10), but an alternative interpretation holds that weight arises only at the level of aggregates. In any case, the properties attributed to atoms are purely geometrical and mechanical — a disciplined ontology that anticipates the mathematical conception of nature in modern science.

4. Sensation and Cognition — "Dark Cognition" and "Genuine Cognition"

Democritus divided cognition into two kinds. "There are two forms of cognition: one genuine (gnēsiē) and the other dark (skotiē)" (DK 68B11). Dark cognition is cognition through the five senses — sight, hearing, smell, taste, and touch; genuine cognition is cognition through reason.

On the mechanism of sensation, Democritus developed a distinctive theory. Thin films (eidōla) constantly stream off the surfaces of objects and, on reaching the sense organs, produce perception (as reported in Theophrastus, De Sensibus 49–83). Vision occurs when these images pass through the air and enter the eye; taste arises from the shapes of atoms acting on the tongue. Round atoms taste sweet; angular atoms taste bitter.

Here, however, an epistemological difficulty emerges. If sensation is merely "convention," then the very means by which we infer the existence of atoms and void ultimately depends on sensation. Democritus himself was aware of this difficulty, as a famous fragment shows. The senses address reason: "Wretched mind, you get your evidence from us, and yet you try to overthrow us? Your victory is your own downfall" (DK 68B125). Reason cannot function without sensation — this self-awareness anticipates the problem-consciousness of modern empiricism.

5. Cosmology — Infinite Worlds and Mechanistic Necessity

Atoms move eternally through infinite void. This motion has no beginning and requires no external cause. Through collisions and rebounds, atoms eventually form vortices (dinē). Within the vortex the principle "like to like" operates — just as sifting grain causes grains of the same size to cluster together (the analogy in DK 68B164) — heavier atoms move to the centre and lighter atoms to the periphery, producing the earth, sea, and celestial bodies (Diogenes Laërtius IX.31–33). Leucippus declared: "Nothing comes into being without reason; all things arise by logos and of necessity" (DK 67B2). Democritus inherited this thoroughgoing mechanistic determinism.

Still more remarkable is Democritus' assertion that infinitely many worlds (kosmoi) exist (as reported in Hippolytus, Refutation of All Heresies I.13). If atoms and the void are infinite, then the patterns of atomic combination are also infinite, and worlds like ours — or utterly unlike ours — can exist in infinite number. This idea calls to mind the multiverse hypothesis of contemporary cosmology.

Yet Democritus' cosmology contains no teleology. Whereas Anaxagoras made Nous (Mind) the cause of cosmic order, Democritus held consistently to a purely mechanistic explanation. Atoms moving without purpose or design produce, as a result, an ordered world — a viewpoint that underlies the methodology of modern science.

6. The Origin of Civilisation — A History of Humankind Without Gods

Democritus extended the atomistic framework to explain the development of human civilisation. According to a report preserved by Diodorus Siculus (Bibliotheca Historica I.8) — a passage widely believed to draw on Democritus — early humans lived scattered like beasts, gathering fruits. The threat of wild animals drove them to cooperate, and language, fire, and technology were gradually invented out of necessity (chreia). Civilisation was not bestowed by gods or heroes; it was born of human experience and trial and error — a naturalistic account of civilisation that was remarkably advanced for antiquity.

On language, too, a notable view is transmitted. Democritus held that there is no natural connection (physei) between words and things; rather, language operates by convention (thesei) (Proclus, Commentary on Plato's Cratylus XVI). He is said to have offered four arguments for this position: homonyms, synonyms, changes of name, and nameless things. This argument for the conventionality of language is a precursor to the modern discussion of arbitrariness in the philosophy of language.

7. The Atomism of the Soul — Mind as Matter

Democritus held that the soul (psychē) too is composed of atoms. Soul-atoms are spherical and smooth, resembling fire-atoms (Aristotle, De Anima I.2, 403b31–404a16). These finest, most mobile atoms are distributed throughout the body, endowing it with motion and life. Breathing draws in spherical atoms from the external environment and prevents the internal soul-atoms from dispersing. When breathing ceases, the soul-atoms scatter and death ensues.

The implication is clear: the soul is not immortal, and there is no life after death. This stands at the diametrically opposite pole from Plato's attempts to prove the immortality of the soul, and Epicurus would later inherit this position and declare that "death is nothing to us."

8. Ethics — Euthymia (Tranquillity of the Soul)

Democritus left a substantial body of ethical fragments in addition to his natural philosophy. At the centre of his ethical thought stands the concept of euthymia (the good state of the soul, tranquillity of mind). "The best for a human being is to live as cheerfully as possible and to suffer as little as possible" (the import of DK 68B189).

Euthymia is not the maximisation of pleasure. Democritus warned against excessive desire and valued moderation (metriotēs). "He who finds delight in a moderate life will find that want and excess disappear of their own accord" (the import of DK 68B191). He ranked the pleasures of the soul above those of the body, and found the highest joy in the pursuit of knowledge itself. "To discover one cause is better than to become king of Persia" (DK 68B118) — in this single sentence, Democritus' intellectual passion is crystallised.

This ethical thought is intimately connected to atomism. Since the soul, too, is made of atoms, the state of the soul depends on the motion of its atoms. Excessive excitement and desire represent violent motion of soul-atoms; tranquillity represents gentle motion. Ethics is an extension of physics — such a unified worldview is a hallmark of ancient materialism.

Democritus also left rich fragments on social ethics. "Poverty under a democracy is as much to be preferred over so-called prosperity under an autocracy as freedom is to be preferred over slavery" (DK 68B251). Again: "Law exists for the benefit of human life; when it harms, it harms only those who, through their own wickedness, are unfit to enjoy its benefits" (the import of DK 68B248). He emphasised inner shame over external coercion: "Do not be ashamed before others, but before yourself" (DK 68B264). Such an inward-looking morality runs parallel to the ethics of Socrates, and the resemblance between the two thinkers' thought is noteworthy.

Guide to Key Texts

• Democritus (fragments, DK 68) — No complete work survives. Approximately 300 fragments and testimonies are preserved as quotations in later authors (Aristotle, Theophrastus, Simplicius, Stobaeus, among others).
• Great World-Order (Megas Diakosmos) — One of his principal works, treating the generation and structure of the cosmos. Some attribute it to Leucippus.
• Little World-Order (Mikros Diakosmos) — A treatise on the human world and the development of civilisation.
• On Cheerfulness (Peri Euthymiēs) — His central work on ethics. The fact that Seneca's De Tranquillitate Animi bears the same title attests to its influence on later thought.
• Diels, H. & Kranz, W. Die Fragmente der Vorsokratiker (DK) — Democritus is number 68. The fundamental reference for fragment studies.
• Uchiyama Katsutoshi (ed.), Fragments of the Pre-Socratics, vol. III (Iwanami Shoten, 1997) — Japanese translation of DK fragments.
• Taylor, C.C.W. The Atomists: Leucippus and Democritus (Toronto UP, 1999) — English translation and commentary on the fragments and testimonies; the standard scholarly work.

Major Criticisms and Controversies

1. Aristotle's critique: Aristotle subjected atomism to multifaceted criticism. (1) The void does not enable motion but makes it impossible — in a void there is no resistance, so velocity would be infinite (Physics IV.8, 215a–216a). (2) If atoms have weight, how is their first motion in a void to be explained? (3) Differences in atomic shape alone cannot fully account for the diversity of sensory qualities.

2. Plato's implicit opposition: Plato never criticises Democritus by name, but the cosmology of the Timaeus — a teleological cosmology in which the Demiurge (Craftsman) fashions the world — can be read as a counterproposal to Democritus' mechanistic cosmology. The world possesses order not by accident but by intelligence — a claim that constitutes a fundamental objection to materialism.

3. The problem of epistemological self-refutation: Dismissing sensation as mere convention while relying on inferences from sensation to establish the existence of atoms — this circularity has been noted since antiquity. The passage DK 68B125, cited above, shows that Democritus himself took this problem seriously.

4. Epicurus' modification: The successor Epicurus inherited Democritus' atomism but introduced an important modification. Against Democritus' strict determinism, Epicurus introduced the atomic "swerve" (parenklisis; Latin clinamen) to create room for free will. If everything is determined by necessity, moral responsibility cannot exist — a criticism that anticipates the fundamental problem of free will versus determinism in the history of philosophy.

5. Modern interpretive controversies: To what extent does Democritus' atom overlap with the atom of modern science? Important differences exist: the modern atom is divisible (into protons, neutrons, and electrons), and at the subparticle level particles exhibit wave–particle duality. Nevertheless, the fundamental idea that "the world is composed of discrete basic units" and the methodological commitment that "sensory qualities can be reduced to physical structures" are strikingly consonant with the modern outlook.

Influence and Legacy

The Epicurean School: Democritus' greatest successor was Epicurus (342–270 BCE). Epicurus adopted atomism wholesale and, in ethics, developed euthymia into ataraxia (freedom from disturbance). The Roman poet Lucretius set out atomism in the grand didactic poem De Rerum Natura (On the Nature of Things).

The Scientific Revolution: During the Scientific Revolution of the seventeenth century, Democritus' atomism attracted renewed attention. Gassendi revived Epicurean atomism; Boyle applied it to chemistry as corpuscular philosophy. Newton, in Query 31 of the Opticks, wrote that God originally created "solid, massy, hard, impenetrable, moveable particles."

Modern philosophy: Democritus' distinction between primary and secondary qualities is directly reflected in Locke's epistemology. Locke treated shape, size, and motion as primary qualities (objective) and colour, taste, and sound as secondary qualities (subjective). The prototype of this distinction is Democritus' contrast between "by convention" and "in truth."

Marx: Karl Marx's doctoral dissertation (1841) was entitled The Difference Between the Democritean and Epicurean Philosophy of Nature. Marx contrasted Democritus' determinism with Epicurus' introduction of freedom, and discussed the relationship between materialism and human liberty. This early study can be read as the germ of his later historical materialism.

Modern science: From Dalton's atomic theory (1803) through Rutherford's nuclear model (1911), the existence of atoms was experimentally confirmed. The modern atom differs from Democritus' atom, of course, but the fundamental framework — "the world is built from combinations of basic units" — has changed remarkably little.

Connections to the Present

First, the possibilities and limits of reductionism. Democritus reduced all things to the arrangement and motion of atoms. Modern science likewise attempts to reduce life to DNA base sequences and consciousness to patterns of neuronal firing. Yet "why does consciousness accompany physical processes?" (the hard problem of consciousness) remains unsolved. The path of reductionism that Democritus opened has not yet reached its terminus.

Second, determinism and free will. In Democritus' world everything is necessary and nothing is accidental. The deterministic aspects of the brain suggested by modern neuroscience — Libet's experiments (1983), which show that the brain begins to act before a conscious decision is made — rekindle, in a new form, the problem Democritus raised. Are our actions determined by atoms (or subatomic particles), or is there room for free choice?

Third, the gap between sensation and reality. Democritus' dictum "sweet by convention" resonates with the constructive nature of perception that modern cognitive science has revealed. Colour is the brain's response to a specific wavelength of electromagnetic radiation; sound is the brain's interpretation of vibrations in the air. There is an essential gap between the "true nature" of the world and the world we experience — a recognition that goes all the way back to Democritus.

Fourth, combinatorial science. Democritus' idea that the combinations of atomic shapes, arrangements, and orientations generate all things shows a striking structural parallel with modern molecular biology. DNA's double helix encodes all the diversity of life in the arrangement of just four bases (A, T, G, C). The principle that infinite diversity arises from combinations of a small number of basic units is precisely the intuition Democritus expressed through his analogy with the letters of the alphabet.

Questions for the Reader

• Can a reductionist explanation that decomposes the world into its smallest constituents really explain "everything"? Can the "quality" of colour or emotion be exhaustively captured by physical structure alone?
• If everything in the universe is nothing more than the motion of particles governed by physical laws, what meaning can the pursuit of "the good life" have? Can Democritus' euthymia be adequately grounded within a materialist framework?
• In modern physics, the behaviour of subatomic particles is said to be probabilistic (quantum mechanics). How should Democritus' thoroughgoing determinism be modified in the light of this fact?

References

• (Primary sources): Diels, H. & Kranz, W. Die Fragmente der Vorsokratiker, 6th ed., 1951. (DK 67: Leucippus, DK 68: Democritus) — Standard edition of Pre-Socratic fragments
• (Study): Taylor, C.C.W. The Atomists: Leucippus and Democritus. Toronto UP, 1999. — English translation and commentary on the fragments and testimonies; the standard scholarly work
• (Study): Kirk, G.S., Raven, J.E. & Schofield, M. The Presocratic Philosophers. 2nd ed., Cambridge UP, 1983. — Standard overview including a chapter on the Atomists
• (Study): Hasper, Pieter Sjoerd. "Leucippus and Democritus." In The Oxford Handbook of Presocratic Philosophy, eds. Patricia Curd & Daniel W. Graham. Oxford UP, 2008. — Comprehensive treatment of atomism
• (Japanese): Uchiyama Katsutoshi (ed.), Fragments of the Pre-Socratics, vol. III. Iwanami Shoten, 1997. — Japanese translation of DK fragments
• (Study): Berryman, Sylvia. "Democritus." Stanford Encyclopedia of Philosophy. https://plato.stanford.edu/entries/democritus/
• (Study): Marx, Karl. Differenz der demokritischen und epikureischen Naturphilosophie, 1841. — Marx's doctoral dissertation on atomism and freedom
• (Overview): Aristotle, Metaphysics I.4; On Generation and Corruption I.2, I.8; De Anima I.2 — The most important ancient testimonies on Democritus' atomism