Pluralism and Atomism in Ancient Greek Philosophy

The Pluralistic School

Speculation about the physical world, initiated by the Ionians, was continued in the 5th century BC by Empedocles and Anaxagoras. They developed philosophies which replaced the description of a first Ionian substance only by the assumption of a plurality of substances. Empedocles maintained that all things are composed of four irreducible elements: air, water, earth, and fire, combined or separated by two opposing forces as a process of alternation: love and hate. Through this process, the world evolves from chaos to form and back into chaos again, in a repeated cycle. Empedocles considered the eternal cycle as the true object of religious worship and criticized the popular belief in personal gods, but failed to explain how objects can be known by the experience developed in isolation from factors that are completely different from them.

Therefore, Anaxagoras suggested that all things are composed of tiny particles or "seeds", which exist in infinite variety. To explain how these particles combine to form the objects that constitute the known world, Anaxagoras developed a theory of cosmic evolution. He claimed that the active ingredient in this evolutionary process is a universal mind that separates and combines the particles, the nous. The concept of elementary particles led to the development of an atomic theory of matter.

Atomistic School

It was a natural step that led from pluralism to atomism, the interpretation that all matter is composed of tiny indivisible particles that differ only in simple physical properties such as weight, size, and shape. This step was taken in the 4th century BC by Leucippus and his most famous collaborator, Democritus of Abdera, who was credited with the first systematic formulation of an atomic theory of matter. His conception of nature was an absolute materialist, explaining all natural phenomena in terms of the number, shape, and size of atoms. He reduced sensory qualities of things (such as heat, cold, taste, and smell) to the quantitative differences of the atoms. The higher forms of existence, such as the life of plants and animals and even humans, were explained by Democritus in strictly physical terms.

He applied his theory to psychology, physiology, the theory of knowledge (epistemology), ethics, and politics, and thus presented the first comprehensive approach of deterministic materialism that asserts that all aspects of existence are rigidly determined by physical law.