The pre-Socratic philosophers were thinkers within the Western intellectual tradition (mostly) preceding the life Socrates (c. 469 – c. 399 BC) living in Ionia (coast of modern day Turkey), Italy, and Greece. Some of these thinkers were also contemporaneous with Socrates, such as Democritus (460-371 BC) and Parmenides (510-450 BC). There are three pre-Socratic schools: the Ionians (holding to corporeal monism), Italians (incorporeal monism), and Athenians (corporeal pluralists).
The Ionian Philosophers
There were four major thinkers from Ionia: Thales of Miletus (624 – 546 BC), Anaximander (610 – 547 BC), Anaximenes (585 – 528 BC), and Heraclitus (535 – 475 BC), all of whom are united by four common beliefs. First, they were naturalistic in outlook. They sought naturalistic explanations as opposed to supernatural explanations involving the gods. This was a dramatic turn in an ancient world in which polytheism (belief in many gods) and the influences of the gods in human affairs was widely believed. The Ionians, one might say, were the first natural scientists. Secondly, they were all materialists. They believed that all that exists is material matter, and that this matter is eternal. Third, they were corporeal monists, the conviction that all existing things can be reduced to one common substance, although the Ionians disagreed on what this substance is. Fourthly, they were hylozoists in that they all subscribed to the idea that there is a form of life in all material objects.
Thales of Miletus is hailed as the first natural scientist and the individual with whom western philosophy begun. He was also a noted mathematician and businessman, and possessed a good understanding of geometry and astronomy, which included him predicting an eclipse of the sun in 585 BC. It is further believed that while in Egypt, Thales measured the height of the Great Pyramids via their shadows. He could calculate the distance that ships were from shore, and he theorized concerning the size of the sun and moon as well as the cause of earthquakes. He is most reputable for his belief that water is the basic substance of all things. Everything is made from water, which he saw is a fundamental and important part of human existence. Water is required for survival and without it things die. It can also to take three different forms: solid, liquid, and gas, and all things constitute one of these three forms.
Anaximander, whose work touches on the fields of metaphysics, geography, biology, and astronomy, was a student of Thales, and his answer to the question of substance disagreed with his teacher’s idea of water. He used the term apeiron (the boundless) to denote an undefined substance behind everything. All things originate within this substance to which life returns when it dies. Whatever the boundless is, Anaximander describes it as unlimited, immortal, unborn, and impersonal. He was also the first evolutionist in that he posited the first creatures to have originated from a moist element by evaporation, and that human beings originated from some other kind of animal. Material gradually developed into different forms, of which the human being is one such form.
Anaximenes believed that the fundamental substance is air, and that all existing things were at some point air before natural forces acted upon them. When it was acted upon, air transformed it into other materials, which constitutes Anaximenes’ theory of the origin the world. Anaximenes also posited wind, cloud, and water to be modifications of the substance of air, and not distinct substances. He further explained meteorological observations (such as thunder and lightning, hail, rainbows, and earthquakes) on observational and experiential grounds, viewing them as natural phenomena.
Heraclitus, sometimes called the weeping philosopher of Ephesus (a result of his melancholic disposition), said the fundamental substance is everliving fire. He also famously quipped that one never steps into the same river twice, a notion predicated on his conviction that all things are in flux and therefore changing. Despite all things being in this state of flux, the world itself still remains stable, and although parts of it are consumed by fire at any given time, the whole remains. Heraclitus also introduced the term and concept of logos, according to which all things are one.