section_path: Western/Ancient/Presocratic
section_name: Presocratic
paragraph_text: Presocratic
  
  The first period of Ancient Greek philosophy is known as Presocratic philosophy, which lasted until about the mid-4th century BCE. Studying Presocratic philosophy can be challenging because many of the original texts have only survived in fragments and often have to be reconstructed based on quotations found in later works.
  
  A key innovation of Presocratic philosophy was its attempt to provide rational explanations for the cosmos as a whole. This approach contrasted with the prevailing Greek mythology, which offered theological interpretations—such as the myth of Uranus and Gaia —to emphasize the roles of gods and goddesses who continued to be worshipped even as Greek philosophy evolved. The Presocratic philosophers were among the first to challenge traditional Greek theology, seeking instead to provide empirical theories to explain how the world came into being and why it functions as it does.
  
  Thales (c. 624–545 BCE), often regarded as the first philosopher, sought to describe the cosmos in terms of a first principle, or arche. He identified water as this primal source of all things. Anaximander (c. 610–545 BCE) proposed a more abstract explanation, suggesting that the eternal substance responsible for the world's creation lies beyond human perception. He referred to this arche as the apeiron, meaning "the boundless".
  
  Heraclitus (c. 540–480 BCE) viewed the world as being in a state of constant flux, stating that one cannot step into the same river twice. He also emphasized the role of logos, which he saw as an underlying order governing both the inner self and the external world. In contrast, Parmenides (c. 515–450 BCE) argued that true reality is unchanging, eternal, and indivisible. His student Zeno of Elea (c. 490–430 BCE) formulated several paradoxes to support this idea, asserting that motion and change are illusions, as illustrated by his paradox of Achilles and the Tortoise.
  
  Another significant theory from this period was the atomism of Democritus (c. 460–370 BCE), who posited that reality is composed of indivisible particles called atoms. Other notable Presocratic philosophers include Anaximenes, Pythagoras, Xenophanes, Empedocles, Anaxagoras, Leucippus, and the sophists, such as Protagoras and Gorgias.