Democritus of Abdera (472/457-370/360 BC) pre-Socratic Greek philosopher and the father of atomic theory. Democritus published works on ethics, physics, mathematics, cosmology and music. Very little has survived but his theories are known through commentaries on his work by later philosophers. In his atomic theory he stated that matter is made up of tiny invisible particles called atoms. The properties of different substances were determined by the physical features of the atoms. For instance, atoms of water were smooth and round whilst atoms of fire were thorny. He believed that the motion of atoms was dictated by definite universal laws of nature and not by the will of the Gods. His birth and death dates are unknown, but it is generally agreed that he died of old age, some believing him to have lived over 100 years. Engraving by J.W. Cook, 1825.