Parmenides of Elea was a pre-Socratic Greek philosopher from Elea in Magna Graecia. Parmenides has been considered the founder of ontology or metaphysics and has influenced the whole history of Western philosophy.[1]
In these early days most philosophers held that the earth was composed of four elements - earth, water, fire and air; but one thinker, called Democritus, a native of Thrace, explained the structure of the universe in another way. He said that it was made up of infinitely minute particles differing from each other in size, weight, shape, etc., and that these particles were indivisible, invisible, and indestructible - "atoms", he called them, i.e., particles that could not be cut in two, as the word means. At the beginning the atoms were in constant motion, but by and by they came together by chance and united in various ways to form solids, liquids and gases.[2]
Democritus, by contrast, wrote prolifically, producing over eighty known treatises, none of which have survived to the present day complete. However, a massive number of fragments and quotations of his writings have survived. These are the main source of information on his teachings about atoms. Democritus's argument for the existence of atoms hinged on the idea that it is impossible to keep dividing matter infinitely - and that matter must therefore be made up of extremely tiny particles.[3]
Democritus believed that atoms are too small for human senses to detect, that they are infinitely many, that they come in infinitely many varieties, and that they have always existed. They float in a vacuum, which Democritus called the "void", and they vary in form, order, and posture. Some atoms, he maintained, are convex, others concave, some shaped like hooks, and others like eyes. They are constantly moving and colliding into each other. Democritus wrote that atoms and void are the only things that exist and that all other things are merely said to exist by social convention. The objects humans see in everyday life are composed of many atoms united by random collisions and their forms and materials are determined by what kinds of atom make them up. Likewise, human perceptions are caused by atoms as well. Bitterness is caused by small, angular, jagged atoms passing across the tongue; whereas sweetness is caused by larger, smoother, more rounded atoms passing across the tongue.[3]
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