Empedocles

In the 5th century BC Empedocles classified all substances as combinations of four elements: air, earth, fire, and water. In the 4th century BC Aristotle reiterated this, emphasizing that these four elements are bearers of fundamental properties.

When looking at the physical world, the most striking basic differences are those between solids, liquids, gases, and fire. These observed differences must be accounted for by any scientific theory of nature. Empedocles' theory was a natural extension of this. This theory dominated physics and chemistry until the 17th century.

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