Heraclitus (540–480 B.C.)
Heraclitus of Ephesus was a Pre-Socratic philosopher who believed that the central element in the world was fire. He is most famous for his assertion that the world is in a constant state of flux. For Heraclitus, nothing stays the same, and he likened the world to a flowing stream that is never the same from one moment to the next. Thus, the famous statement, “You can’t put your feet in the same stream twice.”