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460 BCE
Void hypothesis
Any movement would require a void, which would be nothing, but nothing cannot exist. The Parmenidean position was "You say there is a void; therefore the void is not nothing; therefore there is not the void". This position is validated by the observation that where there seems to be nothing there actually is air, even where there is not matter there is something -
442 BCE
The atomic theory
The theory of Democritus states that everything is composed of "atoms", which are physically but not geometrically indivisible. An empty space lies inbetween atoms. Atoms are indestructible and will always be motion; thereis an infinite number of atoms and of kinds of atoms, which differ in shape and size. -
442 BCE
Epistemology
According too Democritus, the knowledge of truth is difficult, since the perception through our senses is subjective. The same senses can give people different impressions, so we cannot judge the truth though senses because senses leave room for omission and error -
442 BCE
Democritus theory of perception
Democritus' theory of perception claims that thin layers of atoms are constantly sloughed off from the surfaces of macroscopic bodies and carried through the air. Visible properties of macroscopic objects, like sizes and shapes, are presented by these films.