Democritus (c. 460 - c. 370 BCE)
Leucippus (5th century BCE)
Atomism is the philosophical position that the universe is composed of fundamental indivisible components known as 'atoms.'
These kinds of thoughts appeared in both ancient Greek and ancient Indian thought.
Democritus's name means 'chosen of the people.' None of his work has survived. Modern scholars doubt the accuracy to many of the anecdotes to Democritus's life. Some writers claimed that he lived to be very old, perhaps more than 100 at the time of his death.
The theory of Democritus held that everything is composed of 'atoms.' Atoms are physically, though not geometrically, indivisible. Between atoms would lie empty space. Atoms were indestructible, have always been and always will be in motion. The atoms, which are infinite in number, differ in shape and size.