Early Greek Philosophy: Ionian Physics (Natural Philosophy). The Milesians and Heraclitus of Ephesus

Ionian Cosmogonies: The Doctrine of the Origins of the World

Building upon the logic of mythology, which primarily concerned itself with the origins of the gods (theogony) and only secondarily with the origins of the world, early philosophers shifted their focus. Unlike mythologists who sought the source of the world's origins in the divine, these early thinkers sought it within nature itself, looking for a principal or ruling element—an arche (from the Greek "archē," meaning to lead or rule)—that could serve as the fundamental substance or force from which everything arises. Each philosopher proposed a different material element as this primary principle.

The scant fragments of Ionian thinkers' writings and later testimonies about their views reveal that their conceptions of the world’s origin combined both genetic and substantial aspects of the arche. In other words, the arche was both the source or "genesis" of all things and their material foundation (substance or "hypokeimenon," meaning "that which lies beneath"). For example, Aristotle notes in his "Metaphysics" that most early philosophers considered the arche to be a material substance from which everything is composed and into which everything eventually dissolves. We will approach the Ionian philosophers' conceptions of the arche from this perspective, noting that the earliest philosophers from Miletus were essentially monists, accepting only one single principle of the world.

Thales, according to the accounts, considered water to be the fundamental principle of everything. Although detailed data on Thales’s views is lacking, hints of the genetic aspect of his principle can be seen in the reasoning behind choosing water as the arche. Aristotle’s opinion suggests that early Greek philosophers associated the generative power of living things with their moisture. Thus, Thales’s choice of water can be understood in this context.

Regarding the substantial nature of water, it can be seen as both the substance constituting things and, in a more physical sense, as the support holding up the earth, since Thales adhered to ancient beliefs that the earth floats on water, like a raft or ship. Some philosophers argue that this position has not only philosophical and cosmological significance but also a natural scientific one. For instance, Karl Popper suggested that Thales's notion of the earth floating on water was a scientific intuition leading to Wegener's theory of continental drift.

Anaximander, the next philosopher from Miletus, posited that the arche was an indefinite or boundless substance (apeiron). The genetic aspect of the apeiron is well-expressed in both its terminology and Anaximander’s cosmological model. The apeiron is described as the source from which all things arise, as it must be infinite to ensure that the process of generation does not come to an end. Anaximander’s thought was focused not on the essence of things but on their origin.

Anaximander's cosmogony is particularly illustrative. He described the origin of the world as the separation of a "generative principle" (gonomon), capable of producing warmth and cold. From these emergent elements of warmth and cold arise the physical elements of the world: air surrounds the earth, and the air is enveloped by a fiery sphere—this solar ring emits fire through an aperture resembling a bellows. In this model, the apeiron is an abstract, undefined substance. Anaximander did not define it as air, water, or any other specific substance but as a general principle from which everything originates.

The third philosopher from Miletus, Anaximenes, proposed that air was the fundamental principle. He explicitly engaged with his predecessors, Thales and Anaximander, arguing that air preceded water and was a concrete, albeit indefinite, principle. Anaximenes’s views are significant as they show a departure from mythological remnants towards more scientific explanations. Air is described as the substance that transforms into other material entities through its motion or internal changes, resembling physical or thermodynamic processes.

According to Anaximenes, air as the principle supports and sustains the world. It is compared to human breath, which binds the body together. However, in Anaximenes’s framework, air does not retain the characteristics of a living entity but rather acts as a material substance undergoing transformations that produce other elements, such as earth, water, and fire.

Heraclitus, one of the most famous Ionian philosophers from Ephesus, continued the tradition of searching for a material principle but chose fire as the arche. He viewed fire both as a substance and as a process of transformation. Fire is seen as the fundamental nature underlying all things and is described as a "living fire," highlighting its eternal motion and change, akin to living organisms. Heraclitus’s view of fire involves both physical and metaphorical aspects, with fire undergoing cyclical changes: it transforms into air, then into water, and finally into earth. This cyclical process reflects Heraclitus’s dialectical view of the cosmos, where opposites are in constant flux and transformation.

In summary, the Ionian philosophers' theories about the origins of the world revolve around two main models: the biomorphic (where the world arises from a life-giving principle) and the physical-mechanical (where the cosmos is formed through processes of condensation and rarefaction). These early ideas laid the groundwork for the subsequent development of philosophy and science in ancient Greece.