Heraclitus (c.540–c.480 BC)
Authors: Long A.A. 
Published: September 2018

No Greek philosopher born before Socrates was more creative and influential than Heraclitus of Ephesus. Around the beginning of the fifth century bc, in a prose that made him proverbial for obscurity, he criticized conventional opinions about the way things are and attacked the authority of poets and others reputed to be wise. His surviving work consists of more than 100 epigrammatic sentences, complete in themselves and often comparable to the proverbs characteristic of ‘wisdom’ literature. Notwithstanding their sporadic presentation and transmission, Heraclitus’ sentences comprise a philosophy that is clearly focused upon a determinate set of interlocking ideas.
As interpreted by the later Greek philosophical tradition, Heraclitus stands primarily for the radical thesis that ‘Everything is in flux’, like the constant flow of a river. Although it is likely that he took this thesis to be true, universal flux is too simple a phrase to identify his philosophy. His focus shifts continually between two perspectives – the objective and everlasting processes of nature on the one hand and ordinary human beliefs and values on the other. He challenges people to come to terms, theoretically and practically, with the fact that they are living in a world ‘that no god or human has made’, a world he describes as ‘an ever-living fire kindling in measures and going out in measures’ (fr. 30). His great truth is that ‘All things are one’, but this unity, far from excluding difference, opposition and change, actually depends on them, since the universe is in a continuous state of dynamic equilibrium. Day and night, up and down, living and dying, heating and cooling – such pairings of apparent opposites all conform to the everlastingly rational formula (logos) that unity consists of opposites; remove day, and night goes too, just as a river will lose its identity if it ceases to flow.
Heraclitus requires his audience to try to think away their purely personal concerns and view the world from this more detached perspective. By the use of telling examples he highlights the relativity of value judgments. The implication is that unless people reflect on their experience and examine themselves, they are condemned to live a dream-like existence and to remain out of touch with the formula that governs and explains the nature of things. This formula is connected (symbolically and literally) with ‘ever-living fire’, whose incessant ‘transformations’ are not only the basic operation of the universe but also essential to the cycle of life and death. Fire constitutes and symbolizes both the processes of nature in general and also the light of intelligence. As the source of life and thought, a ‘fiery’ soul equips people to look into themselves, to discover the formula of nature and to live accordingly.
The influence of Heraclitus’ ideas on other philosophers was extensive. His reputed ‘flux’ doctrine, as disseminated by his follower Cratylus, helped to shape Plato’s cosmology and its changeless metaphysical foundations. The Stoics looked back to Heraclitus as the inspiration for their own conception of divine fire, identifying this with the logos that he specifies as the world’s explanatory principle. Later still, the neo-Pyhrronist Aenesidemus invoked Heraclitus as a partial precursor of scepticism.