Philosophers of Cosmology in Ancient Greece: The Milesians

Written by Kat Jivkova. The Ancient Greeks have been typically associated with philosophy, yet what do they have to say about cosmology? The Milesian philosophers offer insight into early thought on the Universe.

While the Greeks are known mostly for their development of elaborate philosophy led by Plato and Aristotle, what is less known is that these thinkers, along with many others, were entangled in early cosmology. At this time, the boundary between art and science was non-existent, which essentially created an opportunity for rationale to be combined with poetry. Philosophy and science were thus interlinked and enabled natural phenomena to be explained in a way that blunt facts could never illustrate.

The origins of modern cosmology undoubtedly stemmed from Miletus in the fifth century, a city state on the coast of the Aegean Sea. As one of the most powerful Ionian cities of Asia Minor, it thrived in various aspects, particularly commerce and colonisation. However, the city was most distinguished for its scientific, philosophical, and literary figures, all united within the Milesian School. It is here where a revolution in thinking took place, led by a series of individuals who treated physics as an all-encompassing subject, capable of harnessing both poetic and mathematical means of perception.

Indeed, the Milesians primarily understood that by using observation and reasoning, it was possible to correct their world view. This was known as the empirical method and replaced the earlier tradition of storytelling to explain the foundations of the world. This is not to say that imagination vanished – poetry seriously ran rife within this new progression of physics. Some members of the Milesian School developed even more approaches to observation beyond empirics by opting for an avant-garde attitude through the creation of axioms. It was the physicist Thales who epitomised this.

Thales of Miletus was one of the seven sages of Greece, a title given to seven ‘wise men’ in classical Greek tradition. He was a politician, philosopher, and physicist, born during the 35th Olympiad, who paved the way for future Milesian thought. While none of his writings survive, he has been described as extraordinary by many historians of antiquity. Stories describe how he advised navigators to steer according to the constellation of Ursa Minor rather than Major and he is also said to have measured the pyramids of Egypt using his own knowledge of geometry, according to the poet Callimachus. This coincides closely with the idea that he was heavily influenced by Egyptian science – there are accounts of him visiting Egyptian priests to learn of their mathematical knowledge, subsequently enabling him to develop several geometric theorems that are still used today. He did this through a proof by deduction, which involved the creation of a set of axioms, as mentioned above. These are statements which are still assumed to be true and have been used by mathematicians ever since.

Undoubtedly, Thales is most famous for his advancements in cosmology, the study of the origins of the world, and more focally, his emphasis on water. He suggested that the element of water was the building block for the world’s formation, using an image of the earth as a ship resting in an ocean. For him, the ocean was infinite and explained all-natural phenomena, such as earthquakes, and while his observation was far off, he was the first who tried to explain things without the inclusion of supernatural means. His reasoning behind the prominence of water is unclear insofar as we know, though Aristotle proposed that it may have been because water is the source of nourishment of all things and therefore the world itself required a soul – Thales was a philosopher after all.

Anaximander was a student, successor and acquaintance of Thales who carried forth his teacher’s legacy but likewise substantiated various new ideas. He established a way of thinking which acknowledged the discrepancies between art and science but also embraced them. Known to be imaginative and to use anthropomorphic language, his recordings were ostentatious and artistic. While Thales claimed that the earth’s foundation was water, Anaximander created a new cosmological theory of equilibrium; the earth itself was balanced not by an endless ocean but by symmetry, which enabled the sun, moon and stars to encircle it at set distances.

Anaximander further demonstrated his split from Thales’ principles through his belief in the primal substance apeiron, ‘the infinite’, which is what he held everything to be made of. Before the Big Bang Theory existed, came his idea that earth was a product of eternal motion which spun in a rotary motion and separated opposites, such as dark and light. In turn, these interacted with the apeiron to give birth to all living things. This divine cosmological explanation certainly exhibits signs of philosophical thought, since Anaximander believed the apeiron could also destroy the world to pay retribution for the loss of time. Notably the closest thing which resembles the apeiron substance now is the covariant quantum field; these are fields which are capable of generating spacetime by themselves and are a manifestation of a single form of unit, used in the current theory of Quantum Gravity.

Anaximander was not the only Milesian to challenge his predecessor. His own student, Anaximenes, mirrored his earlier actions and once again transformed cosmological thought. He was a Greek philosopher who evidently drew much of his thought from mystical beliefs, which differentiated him from other members of the Milesian School. Following the assumption that aer is what earth was made up of, he insinuated that different air densities related to various types of matter which existed everlastingly in motion. He extended this to a spiritual level by depicting aer as a quality which possessed life and followed a trajectory of chaos. Undeniably, his surreal cosmic theories combined myth and natural processes in a tumultuous manner.

Nevertheless, there were some useful truths in Anaximenes’ work beyond its mystical components. He also stated that natural phenomena had come from the ways in which aer could compress and rarefy. In suggesting so, he was able to show that the elements of the world were not granular but formed a continuous spectrum: aer would become water when condensed but fire when rarefied, for example. This process could potentially be interpreted as an explanation of how particles themselves move apart and closer together, therefore meaning Anaximenes was a pro-atomist depicting the first elementary suggestion of the time.

These three Milesian thinkers were engineers of cosmology, ultimately unifying philosophical thought in pre-Socratic times and scientific theory. Whether it was water, ‘the boundless’, or air which lay the fundamentals for matter is negligible in comparison to what these great thinkers collectively achieved: a new system of thought, started in the cosmos.

Written by Kat Jivkova


Cerri, Giovanni. “The Concept of “Matter” in Archaic Greece, 1: Khaos/Aer in Hesiod’s Theogony.” Peitho Vol.8 (2018): 53-80.

Evans, James. (2020) “Anaximander.” [Online]. [Accessed on 20 September 2020].

Kerr, Anne and Wright, Edmund. A Dictionary of World History (3 ed.). Oxford: Oxford University Press, 2015.

Logan, Robert K. The Poetry of Physics and The Physics of Poetry. Singapore: The World Scientific Publishing Company, 2010.

Mark, Joshua. (2019) “Anaximenes.” [Online]. [Accessed on 20 September 2020].

Priou, Alex. “Going Further on Down the Road. The Origin and Foundations of Milesian Thought.” The Review of Metaphysics Vol.70 (2016): 3-31.

Rovelli, Carlo. Reality Is Not What It Seems: The Journey to Quantum Gravity. London: Penguin, 2017.

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