Democritus as Scientist: Atomic Theory & Model

Instructor: Flint Johnson

Flint has tutored mathematics through precalculus, science, and English and has taught college history. He has a Ph.D. from the University of Glasgow

This lesson will be an explanation of Atomic Theory as laid out by Democritus and his mentor Leucippus. It will also give a background for the theory and the contemporary response. Following the lesson you can test your knowledge with a quiz.

Democritus and Leucippus

Both Democritus and his mentor Leucippus believed in a scientific rationalist philosophy, that is they believed that observation when coupled with reason was the best tool for understanding the world. Both men were also materialists, believing that everything occurred as controlled by natural laws. As a result, their thinking focused on the causes of an event. The alternative school of the time, led by Plato and Aristotle, were more concerned about the purpose or end result.

Previous Theories

There were two main schools of thought regarding the composition of the universe. The first was by Heraclitus and it believed that everything was in a constant state of change. He saw matter as moving through voids to constantly shape and reshape itself, like a house needing open air to be built or a seed needing a void to grow into. Basically, you need empty space in order for something to fill it, right?

The second theory was forwarded by Parmenides. He believed that there was no void and summed his belief up in the statement, 'if the void is, then it is not nothing and therefore there is no void.' Without a void there was nothing to move through in order to move or change. That meant that there could be no change. This theory stated that all observations to the contrary were wrong and in essence, that change was an illusion. Parmenides also believed that our senses could not be used in understanding the universe. The only way to understand was through pure reason.

These two theories were essentially in direct opposition to one another; it was like trying to square the circle. How could anyone possibly find common ground on this? Well, that's where Democritus and Atomic Theory come into play.

What Exactly is Atomic Theory?

Atomic Theory_, or Atomism, took the best of both theories. As it was clear that things did change (like when a dead tree rots while a sapling grows) there had to be change or at least there had to be some explanation for why it appeared that things changed. That suggested there had to be a void. But the idea of things constantly metamorphosing themselves into something different seemed unlikely too. To explain this, Democritus and Leucippus both thought there had to be some sort of object that could not be broken down any further. It was this object, which they termed an atom, that was the basis of all matter in the universe.

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