Heraclitus (hĕrəklĪˈtəs) [key], c.535–c.475 B.C., Greek philosopher of Ephesus, of noble birth. According to Heraclitus, there was no permanent reality except the reality of change; permanence was an illusion of the senses. He taught that all things carried with them their opposites, that death was potential in life, that being and not-being were part of every whole—therefore, the only possible real state was the transitional one of becoming. He believed fire to be the underlying substance of the universe and all other elements transformations of it. He identified life and reason with fire and believed that no man had a soul of his own, that each shared in a universal soul-fire.
See his Cosmic Fragments, ed. by G. S. Kirk (1954, repr. 1962); study by G. O. Griffith (1977).
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