April 14, 1994
Leucippus, born ca. 500 BCE, and his pupil, Democritus, born ca. 460 BCE, are credited with postulating the theory of Atoms and Void. Democritus expanded upon Leucippus' original theory and theorized on many of its detailed applications like perception. Leucippus is credited with writing only a few works, including The Great World System, in which he postulates his theory on atoms and void. Democritus was a much more prolific writer and is credited with writing fifty-two works, although some were quite short. These included his expansion on Leucippus' work in The Little World System, and eight works on ethics. Unfortunately, while his work on ethics comprised only a small portion of his work, nearly all the existing fragments from his work are from the ethical works.
Leucippus' theory was a reaction to the theories of Parmenides and Zeno; it was an attempt at a reconciliation of elliptic principles and our senses. Parmenides and his pupil, Zeno, believed that the formative substance of the universe was the One, an infinite, all encompassing, motionless mass that contained no empty space, void. Leucippus theorized that this theory could not be correct; since our senses tell us that there is motion. He postulated that void, the absence of all anything that exists, is necessary for motion. He also postulated that an infinite number of particles, atoms, forms what exists and that the dissolution of these particles leads to the destruction or death of that object. The use of atoms solves the problem with the Eleatic principle that nothing that truly is can change or come into existence or perish. Only the forms that the atoms comprise are changing; the atoms themselves are changeless and complete within themselves.
The theory on void and atoms developed by the Atomists is developed for us by Aristotle in Metaphysics. The shape and existence of all things are determined by void and atoms through the differences in shape, position and arrangement of the atoms and the proportion of void in the substance. They believed that there was an infinite number of atoms that were indivisible and impassable. These atoms do not contain any void, making them indivisible because void between bodies is necessary to break the bodies apart. The absence of void makes the atoms incredible compact, weighing a lot proportional to their size. Since all material is made of atoms, the more dense a material is the less void it contains. An example of this theory is the beliefs about fire; philosophers believed that fire was a state of matter, like water. The Atomists believed that fire contained atoms separated by a large area of void; therefore, fire rises out of the material that produces it.
Both Leucippus and Democritus believed that the senses were not completely reliable in what they report to the mind. However, Democritus developed a critique on the trustworthiness of the senses. He theorized that something is "by convention hot, by convention cold, by convention color; but in reality atoms and void." He was saying that people have decided how to classify things as hot or cold or which color, but in effect what classifies them are the type of atom and the quantity of void. He believed that all senses were the result of touch on various places of the body. Unfortunately, he did not describe the sense of touch and how the imprint would affect the body or how the observer would know the difference between various substances.
Using this basic theory of atoms and voids, Democritus then deduced a cosmogony, or a method for the formation of the universe. Basically, the theory is that atoms in a general area will join into forming a whirl or a vortex. The heavier materials will gravitate to the center and form the earth. The lighter, finer material goes out to the edge of the vortex and eventually ignites due to the intense speed of its revolutions. These lighter atoms would then form the heavenly bodies. Obviously, this is still a geocentric view, but one in which there could be innumerable worlds in the universe, with or without heavenly bodies, or heavenly bodies without worlds.
In these ways, the theory of atomism was able to reconcile the problems with the Eleatic principles of the formative substance when it is compared with the information provided by the senses. It was later used by Epicurus and Lucretius in their own theories on the basic substance of the universe. In the modern world, it helped lead to the development of modern atomic theory; although, the modern theory has a much different belief in the nature of the atom. Modern theorists believe that the atom is almost completely void with a very dense center, instead of the atom being completely solid without any void.
