Democritus was a philosopher born in Abdera around 460 BC. He came from a rich family, so that to allow him to study and travel to Egypt, India, Ethiopia and Athens, where he knew the Socratic and Sophistic culture, which will be very important in his philosophical method.
He believed in the distinction between appearance and reality, which can be explained as an opposition between sensitive knowledge – also called obscure – and rational knowledge – named genuine. It means that reason captures the being of the world, that is, of the atoms including in it; while the senses identify things only superficially. Democritus stated that sensitivity and intellect have equal importance, declaring that knowledge develops in three steps: observation of things through the senses, intellectual elaboration of perceptions through reason, explanation of what the senses show only superficially.
The philosopher was a pupil of Leucippus of Miletus and together they developed a doctrine that is atomism, since it describes the universe as an infinite number of atoms, which are full, immutable, ingenious and eternal. There aren’t any qualitative differences, because atoms are all made of the same matter. The quantitative variety is marked by shape, size and arrangement of atoms.
Over the centuries, Democritus’s atomic system had a considerable scientific relevance. Firstly, a close collaboration is established between senses and reason to investigate, given that the task of the intellect consists in explaining what the senses merely perceive. Therefore, the approach of scientific research is anticipated, although it was improved in the modern era. Secondly, Democritus grasped the idea of the atomic structure of matter, which was taken up in contemporary age taking into account an experimental basis. Democritus also believed that everyone must focus on the cause of phenomena and not on the purpose, in order to better study the matter. Finally, he thought that a philosopher should not consider the quality of things, but their quantitative structure and, therefore, their concrete properties by excluding any mythological element to explain reality.