Heraclitus of Ephesus
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'. 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. Heraclitus appears to have spent his life in Ephesus, which had been founded as a Greek colony some 200 years before his birth. According to ancient biography he was an arrogant and surly aristocrat, given to eccentric behaviour, but these anecdotes are largely a fictional construction built out of his own words, in which the tone he adopts in relation to other people is contemptuous. Rather than viewing this as a psychological trait, it is better to treat it as an extreme instance of the way early Greek poets and sages claimed authority for their work. Heraclitus, however, is exceptional in the explicit contempt he expresses for such hallowed authorities as Homer and Hesiod, and also for the contemporary intellectuals Xenophanes, Hecataeus and Pythagoras. He may have been on bad terms with his fellow citizens for political reasons, including perhaps support he received from King Darius of Persia, and it is likely that he was opposed to the democratic constitutions some Greek communities were beginning to adopt.
Although Heraclitus presents himself as uniquely enlightened, he was clearly familiar with the leading thinkers of his time. He draws attention to the relativity of judgments and the difference between humans and animals in ways that recall Xenophanes' critique of religious beliefs. He almost certainly knew and rejected Pythagoras' doctrine of the transmigration of souls (see Pythagoras). His cosmology is both indebted to and a criticism of Milesian science: the criticism appears particularly in his denial of the world's beginning, but his focus on the law-like processes of nature has clear affinities with Anaximander's celebrated doctrine of cosmic justice.
Heraclitus' work does not survive as a continuous whole. What we have instead is a collection of more than 100 independent sentences, most of which are ad hoc citations by authors from the period AD 100300. Plato and Aristotle rarely cite Heraclitus directly, but their interpretations of him, which are influenced in part by their own preconceptions, shaped the ancient tradition of Heraclitus as exponent of universal flux and of fire as the primary material. Interpretation of Heraclitus is further complicated by the work of his professed follower Cratylus, and still more so by the way Stoics and Pyrrhonists looked back to him as a precursor of their own philosophies. This afterlife is important as an indication of Heraclitus' complexity and capacity to influence a range of very different thinkers, but modern interpretation of him rightly treats it as secondary to the evidence of his own words.