Democritus was a pre-Socratic Greek philosopher from Abdera who formulated an atomic theory of the universe. He believed that everything is composed of invisible, indivisible atoms moving through empty space, and that the qualitative differences between objects result from differences in the shape, size, and arrangement of their constituent atoms. Democritus traveled widely to learn from various cultures and developed the view that sense perceptions are unreliable but true knowledge can be attained through reason and analysis of empirical observations. He proposed that there are two types of knowledge - legitimate knowledge gained through reason and illegitimate knowledge based on subjective sense perceptions. Democritus made contributions to mathematics and proposed theories about the shape of the earth, the structure of the cosmos, and