As far as we know, Heraclitus and Parmenides were contemporaries: Heraclitus was from Asia Minor, and Parmenides was from Southern Italy. We think Heraclitus remained in his hometown of Ephesus all his life. He lived perhaps sometime around 500 BC.
According to the popular Western imagination, Heraclitus is often portrayed as a weeping, brooding philosopher. In Raphael’s famous “School in Athens” Heraclitus is shown off-center, in the corner and alone, while every other thinker is engaged in communication.
According to Eva Brann, in her book Logos, Heraclitus’s teaching is unique among the pre-Socratic philosophers. He believes the world can be explained by means of the logos – explanation, reason, mathematics, or “rationality” (the Latin translation) which is the principle of exchange. The world behaves, or perhaps can merely be explained, by means of laws. There is regularity to the chaos. That regularity is identified as a playful ‘cosmic fire.’ Heraclitus compares the fundamental element of the world to “fire” (many latter historians of philosophy have interpreted this comparison literally, a la Bertrand Russell’s naive materialism in The History of Western Philosophy). Aristotle includes Heraclitus among the physikoi -the investigators of the physical world. The Heraclitean fire is like a transformative substance, the well-spring of a certain ordered chaos to the cosmos.
In addition, Nietzsche provides some unfinished notes on five Greek philosophers in Philosophy in the Tragic Age of the Greeks in 1873. In it, he describes Heraclitus’s philosophy as a kind of Kantian intuitive thinking which perceives the world of opposites (i.e. all objects exist in relation to one another) but that they each emerge out of one continuous action, or strife. All things come to be, temporarily, and then pass into cosmic fire. Heraclitus represents the harmony of two seeming antinomies: law and flux. All that remains of Heraclitus’s thinking is 131 mysterious aphorisms captured in various texts. From what we can gather from his surviving texts, “Becoming” not “being,” takes precedence in Heraclitus -he denies any fixed, immutable “being” (Nietzsche paraphrases Heraclitus’s famous maxim as: “You use names for things as though they rigidly, persistently endured; yet even the stream into which you step a second time is not the one you stepped into before”). The logos post Heraclitus has had a memorable career throughout Western thought: from Plato, to the Bible (particularly in the Gospel According to John) and Plotinus, and through Nietzsche.