Democritus was a pre-Socratic Greek philosopher (born at Abdera in Thrace around 460 BC; died in 370 BC). Democritus was a student of Leucippus, and co-originator of the belief that all matter is made up of various imperishable indivisible elements which he called "atomos", from which we get the English word atom. It is virtually impossible to tell which of these ideas were unique to Democritus, and which are attributable to Leucippus.

Democritus is also the first philosopher we know who realized that what we perceive as the Milky Way is the light of distant stars. Other philosophers, including later Aristotle, argued against this. Democritus was among the first to propose that the universe contains many worlds, some of them inhabited:

Democritus is said to have had a happy disposition, and is sometimes referred to as the "laughing philosopher," as opposed to Heraclitus, who is known as the "weeping philosopher." In the Divine Comedy Dante sees the shade of Heraclitus in Limbo with those of other classical philosophers.He was also a pioneer of mathematics and geometry in particular.

We only know this through citations of his works - On Numbers, On Geometrics, On Tangencies, On Mapping, and On Irrationals - in other writings, since most of Democritus' body of work did not survive the Middle Ages. Aristotle tells us that his theory of matter, commonly called atomism, was a reaction to Parmenides, who denied the existence of motion, change, or the void. Parmenides argued that the existence of a thing implied that it could not have "come into being", because "nothing comes from nothing". Moreover, he argued, movement was impossible, because one must move into "the void" and (as he identified "the void" with "nothing") the void does not exist and cannot be "moved into".

Democritus agreed that everything which is must be eternal, but denied that "the void" can be equated with nothing. This makes him the first thinker on record to argue for the existence of an entirely empty "void". In order to explain the change around us from basic, unchangeable substance he argued that there are various basic elements which always existed but can be rearranged into many different forms.

He argued that atoms only had several properties, particularly size, shape, and mass; all other properties that we attribute to matter, such as color and taste, are but the result of complex interactions between the atoms in our bodies and the atoms of the matter that we are examining. Furthermore, he believed that the real properties of atoms determine the perceived properties of matter--for example, something that tastes sharp is made of small, pointy atoms, while something sweet is made of large, round atoms; the interactions of those atoms with the atoms of the tongue give the impression of taste. Some types of matter are particularly solid because their atoms have hooks to attach to each other; some are oily because they are made of very fine, small atoms which can easily slip past each other.

In Democritus' own words, "By convention sweet, by convention bitter, by convention hot, by convention cold, by convention color: but in reality atoms and void."

Democritus' Philosophies

The World

What was real to Democritus consists of the atoms and the "nothing". Atoms are indestructible, eternal, and are in constant motion.They are not all the same as they differ in shape and position. When the atoms move they come into contact with other atoms and form bodies. A thing comes into being when the atoms that make it up are appropriately associated and passes away when these parts disperse. This leaves no room for the intelligent direction of things, either by human or divine intelligence, as all that exists are atoms and the void. Democritus stated, "Nothing occurs at random, but everything occurs for a reason and by necessity."

The Soul

Although intelligence is not allowed to explain the organization of the world, according to Democritus, he does give place for the existence of a soul, which he contends is composed of exceedingly fine and spherical atoms. He holds that,

In this way, he viewed soul-atoms as being similar to fire-atoms: small, spherical, capable of penetrating solid bodies and good examples of spontaneous motion.

Democritus explained senses along these lines, also. Different tastes are a result of differently shaped atoms in contact with the tongue. Smells and sounds are explained similarly. Vision works by the eye receiving "images" or "effluences" of bodies that are emanated.

He stated that, "Sweet exists by convention, bitter by convention, color by convention; but in reality atoms and the void alone exist." This means that senses do not provide a direct or certain knowledge of the world. In his words, "It is necessary to realize that by this principle man is cut off from the real."

Later philosophers use this to assert that any reliable knowledge can be obtained, but Democritus felt differently:

The following excerpts are from Democritus' extensive writings on ethics, of which little remain:

Reference: Melchert, Norman (2002) - The Great Conversation: A Historical Introduction to Philosophy, McGraw Hill.