Leucippus

Leucippus of Miletus was a pre-Socratic Greek philosopher to whom tradition attributes the founding of atomism, the view that reality is made of indivisible particles moving through empty space. His importance lies in being the first known thinker to articulate a clearly material explanation of the world. His name is almost always linked to that of his student Democritus, with whom he is inseparably associated.

Little is known about his life. He is most likely to have been born in Miletus, in the Ionian region of Asia Minor, although Abdera, Elea, Melos and Clazomenae have also been proposed as his home or place of work. According to tradition, he moved to Elea, where he may have been influenced by Parmenides or Zeno, and where he engaged with the Eleatic school. Some sources place the founding of a school in Abdera around 440 or 430 BCE, closely associated with Democritus. Two works are attributed to him, The Great World System and On Mind, but neither has survived. What we know of him comes from later writers such as Aristotle, Theophrastus, Simplicius and Sextus Empiricus, who often fail to separate his ideas from those of Democritus.

His starting point was a response to the Eleatics, who denied the existence of the void and therefore of motion. Leucippus accepted part of their logic but argued that the void does exist, and that it is precisely what makes motion and plurality possible. Full being, he held, is made of atoms, while non-being is the empty space between them. Nothing happens by chance: everything occurs for a reason and by necessity, so the order of the world follows from the collisions and combinations of atoms. In cosmology he proposed an infinite universe in which worlds form within vortices of atoms, and he described the Earth as drum-shaped. As for the soul, he held that it consists of spherical, mobile atoms, and that breathing renews this vital presence. From this he explained perception through thin films of atoms given off by objects.

His influence was considerable. Democritus developed atomism and applied it to many natural phenomena, and later Epicurus took up the idea of atoms and added chance to necessity. His conviction that everything follows natural causes, without divine intervention, broke with traditional explanations and anticipated debates that would reach modern science, although his atoms bore little resemblance to those of modern chemistry.