Based in Miletus, these thinkers searched for the arche —the single primary substance that makes up the universe.

: Widely considered the first philosopher, he proposed that everything is ultimately made of water .

Here is a look at three major "pieces" or schools of thought that laid the groundwork for Western science and logic: 1. The Milesians: Finding the First Substance

Early Greek philosophy, often called "Pre-Socratic," represents the shift from explaining the world through myths to seeking rational, naturalistic explanations.

Heraclitus believed the universe was in a state of constant flux.