Letter to Herodotus

May 21, 2025 | 1,085 words | 6min read

Paper Title: Letter to Herodotus
Link to Paper: https://users.manchester.edu/Facstaff/SSNaragon/Online/texts/316/Epicurus,%20LetterHerodotus.pdf
Date: Ca. 300 BCE
Paper Type: Philosophy
Short Abstract:
In this letter, Epicurus offers a summary of his belief about what the natural world is made of—namely, atoms.

The letter begins with Epicurus telling Herodotus that he has already written extensively and in detail about nature, and that this letter is meant only as a summary of his philosophy. However, he argues that even knowing just the general principles is better than knowing nothing at all. Moreover, he suggests that a holistic approach—an overview—can sometimes be more useful than delving into details, as it provides a broad understanding of the subject.

He begins by emphasizing the importance of clarifying the meanings of words before laying out his ideas, in order to avoid confusion and empty statements. For this purpose, he argues that we should associate words with clear mental images.

Since his philosophy of nature deals with atoms—things we cannot see—he starts by laying out a set of fundamental assumptions:

1. Nothing comes from nothing: Things don’t just appear out of nowhere; they require some kind of seed or basic principle.
2. Nothing goes into nothing: When something breaks down, it dissolves into something—namely, atoms—not into nothingness.
3. The universe is eternal and unchanging: There is nothing outside or beyond the universe that can influence it.

Next, he argues that everything in the universe is made up of two things: bodies and void. Bodies are material things we can see, feel, and touch. Void is the empty space necessary for bodies to move; without it, the entire universe would be filled with solid matter and nothing could move. Apart from bodies and void, nothing else exists. All properties, such as color and heat, are simply effects of bodies.

He then differentiates between two types of bodies: atoms, which are indivisible and unchanging, and compounds, which are made up of many atoms.

Epicurus also holds that the universe is infinite. Everything that is bounded requires a boundary, but since there is nothing outside the universe to act as such a boundary, it must be infinite. The universe contains infinite bodies (atoms and compounds) and infinite void. If the void were infinite but bodies were finite, atoms would drift endlessly and never form anything. If bodies were infinite but the void finite, there would be no space for them to move or exist.

Because the universe is infinite, there is no absolute “up” or “down”—these directions are relative and depend on the observer’s position.

The bodies differ in shape, which explains their physical characteristics, but there are countably many of them, and each shape or compound is composed of many atoms of that kind.

Atoms are constantly moving through the void in different trajectories, sometimes colliding with one another. When collisions occur, bodies are formed. The movement of atoms is eternal and has no beginning—it is inherent to their nature.

Because atoms are infinite, there are also an infinite number of worlds, some of which are like Earth.

Epicurus also introduces what he calls idols—these are images associated with objects that explain how we perceive them. These images are extremely fine and move very rapidly. They preserve the shape and order of an object’s atoms, allowing us to recognize the object. We perceive these idols when they enter us, carrying with them the shape and color of the object, reproducing its qualities within us. Falsehood arises when we add opinion not confirmed by perception to these images.

Sound functions similarly. An object emits a stream of particles that retain the qualities of the sound and present them to us internally. The air itself is not shaped by sound—rather, sound is caused by particles, much like breath. Smell operates in a similar way: we have sense-organs that detect certain particles that carry a particular scent.

However, it is important not to confuse images and atoms. Atoms themselves have only three inherent properties: shape, weight, and size. Bodies exhibit different properties based on how these atoms are arranged—not because the atoms themselves change.

Because a body is finite, it cannot have infinitely many parts—otherwise, it would itself be infinite. Therefore, atoms are the indivisible smallest units and cannot be further subdivided.

All atoms move at the same speed through the void when they do not collide with anything. Their speed is not affected by their size, weight, or direction. The movement of a whole body (a compound) results from internal atomic collisions, not from atoms moving uniformly as a single unit.

The soul, too, is made of fine particles that are spread throughout the body like a mixture of two substances. It is also the source of sensation and thought. Thus, when the soul leaves the body at death, the body loses sensation, while the soul retains it. The soul is not incorporeal—it is something physical; otherwise, it could neither act nor be acted upon. The only incorporeal thing is the void, which allows motion but cannot itself act.

The qualities of a body—such as shape, color, or weight—are neither independent entities nor incorporeal substances, but they are also not material parts in themselves. Rather, the body is an aggregate of qualities that collectively define it as a body. The body and its qualities are interdependent.

Accidents or events are also not part of the body. Although they happen to bodies, they are not incorporeal entities either. They are temporary occurrences without independent existence in the material world. One example of such an event is time, which is a transient occurrence related to bodies and their changing states, not a permanent or independent substance.

There are many worlds, and these worlds do not exist by design—they emerge through the separation or aggregation of matter, undergoing cycles of creation and dissolution. Regardless of the world, all contain living beings and plants; life and vegetation are universal features that emerge from material conditions.

The same applies to human behavior and capacities: they arose from circumstances rather than design. Reasoning abilities came later, and social consensus helped language and culture become standardized.

The nature of science is to discover the true causes of essential facts, and true happiness comes from understanding nature. It is not enough merely to observe phenomena—we must also understand them. Only then can we rid ourselves of anxiety and fear. Much of human mental disturbance arises from our failure to understand the world. By closely analyzing our internal feelings, we can trace them to their source and ultimately free ourselves from them.

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