The document discusses early Greek philosophers known as the pre-Socratics who lived prior to Socrates in the 6th-5th centuries BC. The first pre-Socratic was Thales of Miletus who proposed that water was the fundamental substance that all things originated from. His student Anaximander rejected Thales' view and claimed everything came from an undefined substance called apeiron. Another pre-Socratic, Anaximenes, proposed that air was the fundamental substance.
Subsequent pre-Socratics like Heraclitus believed the world was in a constant state of flux and conflict. Parm