atomism
A highly reductive theory of the structure of the world, in which all things are made of an infinite number of randomly moving indivisible cells (corpuscles).
The Atomists
Leucippus (about whom almost nothing is known) and Democritus (of Abdera, in Thrace, born about 460), held that void (space with no matter) exists (against the Eleatics, who held that what is not there cannot exist) and that this void contains an infinite number of indivisible units (atoma , which means "indivisibles") which are undifferentiated in material but different in size and shape.
By random movements they form vortexes, in which similar atoms come together and form the sensible world. This theory was taken over later by the Hellenistic philosopher, Epicurus.