The document provides an overview of several early Greek philosophers who lived prior to Socrates, known as the pre-Socratics. It discusses their ideas and philosophical questions, including Thales who proposed everything is made of water, Pythagoras who believed in mathematical and numerical principles of reality, and Parmenides who argued that change is an illusion and the true nature of reality is eternal and unchanging. It also summarizes the atomic theory of Democritus and how pre-Socratic philosophers influenced later traditions of Western philosophy.

1. Introduction to Philosophy IS-VNU Mr. Mike Lecture 2

23. Heraclitus