In the 5th century BCE, Leucippus and his pupil Democritus proposed that all matter was composed of small indivisible particles called atoms. Nothing whatsoever is known about Leucippus except that he was the teacher of Democritus. Democritus, by contrast, was a prolific writer, who wrote 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 for infinity and that matter must therefore be made up of extremely tiny particles.