Heraclitus of Ephesus was an important philosopher of the pre-Socratic period, whose main philosophical thesis is that reality is constantly changing.

He is considered one of the most important thinkers of antiquity, having influenced philosophers such as Plato and Hegel.


Although exact knowledge about Heraclitus’ date of birth or death is not available, it is widely accepted that he lived in the city of Ephesus between the 6th and 5th centuries BCE. Furthermore, it is speculated that he was an aristocrat and a descendant of the founders of the city of Ephesus.

Diogenes Laertius reports that Heraclitus was a private man with a strong temperament; he refused to participate in public life; he criticized the citizens of his own city and made fun of Greek philosophers and poets. His misanthropy led him to live isolated in the mountains.

According to an ancient source, the Greek citizens reportedly asked him to draft laws for the city. However, he immediately refused the offer, preferring instead to play with the children in the temple of Artemis.

Because of his haughty personality, the Greeks created various stories with the aim of ridiculing him, making it difficult to distinguish what is true or not about his life.

Heraclitus, by Hendrick Terbrugghen, 1628, via Wikiart.


The main work attributed to Heraclitus of Ephesus is called On Nature. Some fragments of this work remain, in the form of aphorisms. The content of these aphorisms is quite enigmatic, difficult to understand, and this earned Heraclitus the nickname of the Obscure Philosopher.

He wrote his work in an obscure way with the intention of attracting only readers of prestige and influence, and to keep away those unpleasant and mocking readers who believe they are reading something easy, when in fact they understand nothing.

According to Diogenes, the leading historian of the ancient philosophers, Heraclitus’ work dealt with 3 subjects:

  • On the Cosmos;
  • Politics;
  • Theology;


Everything flows

For Heraclitus, everything is in constant transformation. There is nothing in the world that has any ontological stability. That is why he said, πάντα ῥεῖ (panta rhei), that is, everything flows. There is not even one being that is fixed and immovable. This philosophical thesis is known as mobilism.

For him, it was not possible to bathe in the same river twice, because the waters would not be the same, nor would the person be the same. In one of his fragments, he states:

Into the same rivers we step and do not step, we are and we are not.

In the sphere of ideas, Parmenides was Heraclitus’ main opponent, because he defended immobility, that is, the idea that nothing changes.

The harmony of opposites

According to Heraclitus, all change implies the transformation from one opposite to the other. For example, a cold thing becomes hot, and the hot thing cools down again; a healthy person becomes sick, and vice versa.

The world is made up of this war of opposites. He said:

War is the mother and queen of all things.

But this war is also peace and harmony. Everything changes into its opposite, and in this the harmony consists; as if reality is reconciled with itself. He stated:

Everything that is characterized as opposition is reconciled, from different things the most beautiful harmony is born, and everything is born through contrasts.

It is in the war between opposites that we find the meaning of things. Hunger gives meaning to satiety; sickness shows the value of health; tiredness shows how sweet rest is. If there were no injustices, he said, we would ignore the very notion of justice.

The most beautiful cosmic harmony is like a bunch of things thrown together.

The thesis of the harmony of opposites led Heraclitus to be considered the father of dialectics.

Fire as Arche

Heraclitus conceived fire as arche, that is, as the fundamental principle of the cosmos. According to his theory, all things are transformations of fire.

This world, equal to all, none of the gods and none of the men made it; it always was, is and will be an eternal and living fire, rising and fading in just measure.

This is because fire seems to be in constant motion, it is life that is sustained by the death of fuel, it turns everything to ashes, and it represents both necessity and satiety.


This fire is like lightning that governs the cosmos, so it is also Logos (reason, intelligence).

The notion of Logos in Heraclitus is interpreted as constituting reality. Although all things appear to be multiple and distinct, they are united in a large complex and coherent system, in which men themselves are integrated.

Only one thing is wise: to know the thought that governs everything through everything.

Among other things, the Logos is the organizing principle of opposites. It is through the Logos that the opposites harmonize in a proportional and balanced way.

The explicit notion of Logos, that is, reason/intelligence in Heraclitus, is quite innovative compared to the philosophers who preceded him.


The concept of God in Heraclitus’ thought follows the premises of his philosophical thesis of the harmony of opposites. For him, God is day and night, winter and summer, war and peace, etc. In one of the fragments, he says:

To God everything is beautiful and good and just; men, however, judge some things as unjust and others as just.

On the soul

For the Obscure Philosopher, the human soul was fire.

The wise man possessed a drier soul, while the fool had a wet soul.

His philosophy of the soul, coincides with the Orphic ideas. Heraclitus seemed to advocate the idea that the life of the body would be the death of the soul, and the death of the body, life of the soul.

He also advocated rewards or punishments after death.

Synoptic Table

Heraclitus of Ephesus
Birth – DeathVI to V B.C.
WritingsOn Nature
Main ideasHarmony of opposites, logos, fire as arche
Influenced byMilesian School
InfluencedParmenides, Empedocles, Democritus, Plato, Aristotle, Hegel


BORNHEIM, G.A. (Org.). (1998). Os filósofos pré-socráticos. São Paulo: Cultrix.

KIRK, G.S., RAVEN, J.E., & SCHOFIELD, M. (1983). Os Filósofos Pré-Socráticos: história crítica e seleção de textos. Lisboa: Fundação Calouste Gulbenkian.

REALE, G., & ANTISERI, D. (2007). História da Filosofia: Filosofia Pagã e Antiga. Vol. 1. São Paulo: Paulus.


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