ca. 500 B.C.
Heraclitus, born in the city of Ephesus in Asia Minor, was a philosopher* who taught that everything was always changing. He explained his theories in a book, although only a few fragments of his writings survive. His work consisted of a series of short, riddlelike sayings. His lack of clarity in statements such as “the way up and down is one and the same” and “the connections between things are wholes and not wholes” earned Heraclitus the title “the obscure one.”
Heraclitus disagreed with previous thinkers who argued that there is a single, permanent, changeless reality underneath what can be seen. Instead, he claimed that everything in the world is constantly changing and that constant change is necessary to maintain the correct order of things. Like the earlier philosopher Anaximander, Heraclitus held that nature is in a state of never-ending conflict between opposites, such as hot and cold. All of this change and conflict is regulated by a natural law called Logos. Logos also directs the behavior of people.
Heraclitus taught that everything in the world is made up of three elements—fire, water, and air. These elements constantly change into one another. Everything, even the human soul, starts out as fire, which Heraclitus believed was related to the logos. He believed that a soul full of fire was the best, since more of the other elements in the soul meant that the person was closer to death. Heraclitus was unpopular in his day, particularly for his attacks on the religious practices of the Greeks. (See also Philosophy, Greek and Hellenistic.)
* philosopher scholar or thinker concerned with the study of ideas, including science