: He saw fire as the symbol of this perpetual change and the Logos (universal reason) as the law governing it. 3. Parmenides & Zeno: The Illusion of Motion

: He famously noted you cannot step into the same river twice, as new waters are always flowing.

: 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

: Argued the source couldn't be a specific element like water; instead, it was the apeiron —an "unlimited" or "indefinite" substance. 2. Heraclitus : The Philosophy of Change

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

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