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Key People & Ideas


  • The ultimate reality is Water
  • It explains ontology or being
  • It explains the relationship of solids, liquids, or gases
  • It explains motion


  • Air is the answer to the three questions of being, essence and motion


  • No definite substance is “the” answer, so it must be indefinite

Heraclitus of Ephesus

  • Everything that exists is in a state of flux—whatever  is, is changing
  • “You cannot step into the same river twice” was his motto
  • He was a Monist, but saw whatever was the “one” as being dynamic

Parmenides of Elea

  • “Whatever is, is”, or, that which truly exists is not in flux
  • This was counter to Heraclitus by saying that if objects are truly in constant flux, they cannot be said to “be” anything
  • Even if they were once “something”, they are not now because the object changed to something  different 

Zeno of Elea

  • A pupil of Parmenides
  • He made the reductio ad absurdum argument famous
  • His main opponents were the pluralistic Pythag oreans
  • His four arguments against motion were the stories of Achilles and the tortoise, stadium (half-way argument), flying arrow, and moving rows 

Key Concepts

The One and the Many: Explores the relationship between unity and diversity.

Monists: All reality is one (pantheism). God is “the One”

Pluralists: All reality is various, like a multitude of “seeds.” Democritus best summed up this position with his belief that all reality was made up of tiny particles, also called atoms.

Corporeal and Incorporeal Monists: Either one substance or one spiritual entity make up reality.

Corporeal and Incorporeal Pluralists: Either many particles or many spiritual particles make up reality.

Apeiron: A boundless, ageless and infinite material, also known as the “5th Essence”; the being conceived was not personal, but purely transcendent