A Philosophical Study of Epicurean Atomism

On atoms but not the boring kind...

In my first newsletter exploring Epicureanism, Epicureanism: The Basics, I provided a general overview of what philosophy is all about. This time, I’m diving deeper to unpack atomism — the cornerstone of Epicurean thought.

I only wrote a few paragraphs which barely scratch the surface when it comes to understanding the atomism studied by the Epicureans. At first glance, it might seem like a simple, straightforward theory, but beneath that lies a layered and deliberate attempt by Epicurus to build a cohesive framework—one that addressed gaps left by his predecessor, Democritus, and could hold its ground against potential Aristotelian critique.

Before diving into the Epicurean interpretation of atomism, it’s worth pausing to situate Epicureanism within its historical and philosophical context. Understanding the world Epicurus lived in—and the intellectual challenges he faced—sheds light on why he theorised the way he did.

Epicureanism’s Place in History

‘The Stoic world – like the Aristotelian world before it – is a continuum both materially and structurally: materially because it contains no void gaps, structurally because it is infinitely divisible, or divisible at any point. The Epicurean world is discontinuous in both ways: materially to the extent that it consists of bodies separated by void gaps, structurally both because those bodies are themselves unbreakable (‘atoms’) and because at a still lower level there is an absolute unit of magnitude not capable of analysis into parts (the ‘minimum’).’— Sedley

Epicurus wasn’t just counteracting the rising popularity of Stoicism—a school of thought still widely admired today by those seeking solace—he was also attempting to rescue atomism from the shortcomings of Democritus’s earlier theory and defend it against Aristotle’s staunch critiques. Aristotle’s rejection of atomism had aligned with his own anti-void arguments, and his influence carried weight in both his time and the Stoic tradition that followed. To ensure atomism’s survival, Epicurus had to refine it into a framework robust enough to withstand such attacks.

On a side note, I find the intellectual sparring between philosophers, particularly in the ancient world, endlessly fascinating. Tracing these dialogues through time—spotting who challenged or inspired whom—is one of philosophy’s greatest pleasures. If you wanted, you could chart this rich conversation from Aristotle all the way to contemporary thought.

Back to the matter at hand: the Stoics, heavily influenced by Aristotelian and Platonic traditions, developed a sophisticated view of the universe. They rejected the notion of a void, advocating instead for a continuum theory of matter—a seamless, infinitely divisible cosmos governed by logos, the rational principle orchestrating all things. Their philosophy neatly aligned with Aristotle’s anti-atomist stance, reinforcing a worldview that dismissed the necessity of indivisible particles.

In contrast, Epicurus built on the ideas of Democritus, the original atomist, but he introduced key refinements like minima, indivisible units smaller than what Democritus had theorised. Democritus had been criticised for an eliminativist approach that reduced everything to mere bodies in motion, offering little room for cohesion or practical application. Epicurus sought to address these gaps, crafting an atomist theory that was more comprehensive and philosophically defensible.

To place this in a broader context, here’s a simplified timeline of the key players in this philosophical conversation:

Democritus → Aristotle → Stoics → Epicurus

Atoms, Atoms, and More Atoms

Epicureanism aims to dispel fear—fear of gods, fear of death—by explaining the universe as the result of natural processes. According to this view, the world is material, eternal, and governed by natural causes. There is no divinity shaping or interfering with human affairs; the cosmos emerged from nature, not supernatural design.

At the heart of Epicurean thought is atomism: the belief that everything consists of invisible, indivisible atoms moving through empty space, which they call the void. Atoms and void are the fundamental causes of everything. The diversity of the world, from mountains to twins who look almost identical but differ in subtle ways, is explained by the variety of atom shapes and sizes.

“The totality of things consists of bodies and void; bodies are the atoms, indivisible and unchangeable; void is the space where bodies move.” (LS 11A)

Atoms are indivisible. If they could be divided endlessly, the universe would dissolve into nothing. They are the building blocks of everything, combining to form larger structures that can break apart again into their atomic components. Think of atoms as Lego bricks—each different in size and shape. You can build them into a house or a spaceship, then dismantle them back into individual pieces. (And while yes, you could saw a Lego brick in half, that would be breaking it down into its own atomic components—so let's not ruin the analogy!)

All motion in the universe stems from atoms. Motion itself is eternal and uncaused, continuing without beginning or end. Atoms move at the same speed, occasionally colliding or deviating from their paths due to an "atomic blow." Generally, however, they fall downward through the void, driven by their weight.

“Atoms are solid, eternal, and indivisible, for if they could be broken, the universe would dissolve into nothing.” (LS 12C)

However, atoms don’t just move in straight lines. They sometimes swerve (clinamen), a small but critical deviation that allows them to collide and form complex structures. Without this swerve, atoms would fall in parallel lines like raindrops, and nothing in the universe could ever form—not you, not me, not the stars above us.

“Atoms, as they move through the void, swerve a little at unpredictable times and places. This slight deviation is the cause of collisions and the creation of complex things.” (LS 11E)

This swerve introduces an element of randomness into the cosmos. It’s not just a physical necessity but a philosophical one, allowing for the possibility of free will. Without the swerve, Epicureanism would risk falling into determinism, where every event is causally determined and there’s no room for choice or spontaneity. The swerve breaks the chain of strict causation, creating a form of "spontaneous dynamism." Yet this raises a question: if atoms have causal powers, are we truly free moral agents?

The Theory of Generation

The randomness of atomic movement also explains the creation and destruction of worlds. Nature, according to Epicurus, operates without divine purpose. Atoms don’t make decisions; they have no mental properties. Their collisions and combinations are entirely random, giving rise to infinite possible worlds—some flourishing, others decaying.

“If atoms did not swerve, all would fall through the void like raindrops, and nature could never have created anything.” (LS 11H)

“Nature does not shape the universe for human purposes. It moves and combines through atoms, mindless and unplanned.” (LS 12E–F)

This cosmological claim was meant to remove fear of the unknown, replacing it with a naturalistic understanding of the universe. But does it truly comfort? For some, the idea of infinite worlds and the randomness of existence may heighten the existential dread of death and the possibility of being forgotten entirely.

Can We Trust Our Senses?

Epicureans argue that we can. In fact, they claim that error arises not from our senses but from our mind’s judgment of sensory input. Unlike many philosophical traditions that mistrust the senses—asserting, for example, that our eyes deceive us while the mind reveals truth—Epicureanism takes an empirical approach. Sensations are true because they result from the contact of atoms with our senses. Errors occur only when we attach rash opinions or false judgments to these sensations.

“The eyes, ears, and senses are faithful witnesses; errors come from the mind’s rash opinions.” (LS 13D

“All sensations are true, for they arise from the contact of atoms and the void with our senses.” (LS 13A)

For Epicurus, trusting the senses was essential to understanding the world as it truly is—a material, random, and natural universe where the gods play no part, and fear can be dispelled through reason and observation.

Is Epicurean' Atomism a good philosophy?

I don’t want to sway a reader's opinion to subscribe or unsubscribe from atomism. I want to get to the end of the series until I unpack my stance on philosophy. Atomism is just one part of atomism, and a whole theory is needed to make a final conclusion. But for now here are some questions to consider while forming an opinion of Epicureanism:

1. Can the idea of indivisible, eternal atoms offer a foundation for understanding the material world that aligns with modern scientific perspectives on matter?

2. How does atomism challenge fatalistic views and create space for human agency in a seemingly mechanistic world?

3. How does the theory’s emphasis on natural causes foster a sense of control and understanding over life’s uncertainties?

4. Can a purely materialistic framework account for abstract concepts like morality, consciousness, and purpose, or does it reduce them to mere atomic interactions?

5. Could the randomness of atomic interactions lead to a worldview that feels chaotic or nihilistic, rather than ordered and comprehensible?

Key Texts/ Referencing Ancient Texts

Two key texts which I used unpack Epicureanism:

The first is Epicurus’s Letter to Herodotus, which outlines the foundational principles of his philosophy.

The second is Lucretius’s De Rerum Natura (Book 2), a companion piece that offers a stunningly poetic portrayal of atomism, bringing Epicurean ideas to life with vivid imagery and elegance.

When referencing ancient philosophical texts, specific conventions are typically used to ensure clarity, as many works are divided into standard sections or line numbers rather than traditional page numbers. To understand where I am referencing, this is how citations will appear:

As an example, the citation (LS 11A) refers to a specific text or passage found in The Hellenistic Philosophers by A. A. Long and D. N. Sedley, a well-regarded sourcebook for ancient Hellenistic philosophy (and the sourcebook I follow but the links I provided above will also give you free editions of the texts). This book organizes excerpts from ancient philosophical texts (in both Greek/Latin and English translation) alongside commentary.

1. LS: Refers to Long and Sedley, the authors/editors of the sourcebook. This is a standard abbreviation used when citing their work.

2. 11: Refers to the chapter or section number in The Hellenistic Philosophers. Chapter 11 in LS focuses on a specific topic or philosopher—e.g., early Stoicism, Epicurean atomism, or another Hellenistic school.

3. A: Indicates a specific type of passage. In LS, passages are categorised as:

- A: Testimonia—ancient reports or summaries about a philosopher's teachings.

- B: Fragments—direct quotes or excerpts from the philosopher’s works.

- C: Related discussions or interpretations.

Bibliography

These are some of the texts I referred to in this piece and few others if you are interested in reading further:

Bett, R. (2003). The Cambridge History of Hellenistic Philosophy. Cambridge University Press. Chapter: "Hellenistic Physics and Metaphysics." Retrieved from Cambridge Core

O’Keefe, T. (2009). The Cambridge Companion to Epicureanism. Cambridge University Press. Chapter: "Epicurean Atomism." Retrieved from Cambridge Core

Long, A. A., & Sedley, D. (1987). The Hellenistic Philosophers: Volume 1, Translations of the Principal Sources with Philosophical Commentary. Cambridge University Press.

Sedley, D. (1998). Lucretius and the Transformation of Greek Wisdom. Cambridge University Press.

Warren, J. (2002). Epicurus and Democritean Ethics: An Archaeology of Ataraxia. Cambridge University Press.

Barnes, J. (1982). The Presocratic Philosophers. Routledge.

Guthrie, W. K. C. (1962). The Greek Philosophers: From Thales to Aristotle. Harper & Row.