section_path: Influences/Heraclitus and Parmenides
section_name: Heraclitus and Parmenides
paragraph_text: Heraclitus and Parmenides
  
  The two philosophers Heraclitus and Parmenides, influenced by earlier pre-Socratic Greek philosophers such as Pythagoras and Xenophanes, departed from mythological explanations for the universe and began the metaphysical tradition that strongly influenced Plato and continues today. Heraclitus viewed all things as continuously changing, that one cannot "step into the same river twice" due to the ever-changing waters flowing through it, and all things exist as a contraposition of opposites. According to Diogenes Laertius, Plato received these ideas through Heraclitus' disciple Cratylus. Parmenides adopted an altogether contrary vision, arguing for the idea of a changeless, eternal universe and the view that change is an illusion. Plato's most self-critical dialogue is the Parmenides, which features Parmenides and his student Zeno, which criticizes Plato's own metaphysical theories. Plato's Sophist dialogue includes an Eleatic stranger. These ideas about change and permanence, or becoming and Being, influenced Plato in formulating his theory of Forms.