Thales (620-546 BCE) was born in the city of Miletus of Greek Ionia located on the coast of modern-day Turkey. He was active prior to the Golden Age of Ancient Greece and was a thinker of great repute given the number of prominent ancient writers, poets, philosophers, and historians who speak of him. Aristotle, for example, stated that Thales was the founder of natural philosophy.

Thales is appreciated by modern historians for being the first thinker to seek after natural explanations for phenomena and events in the world initially attributed to the gods and heroes. Events in the world, for Thales, were not the result of supernatural intervention but had natural causes that observation and experimentation could discover. Thales is also credited with the ushering in the beginning of Greek astronomy as he speculated concerning cosmological events traditionally believed to involve supernatural entities. For such reasons, Thales solidified the foundations of future philosophical and scientific thought. He is often referred to as the first scientist in the Western tradition.

Thales was the first thinker to propose the philosophy of material monism, the idea that everything in the universe could be reduced to a single substance. As we learn from Aristotle, Thales posited water as this fundamental property. He claimed that all things, including the Earth, came into being from water, and he also said that the Earth is a disk floating or resting on top of water.

Although historians know Thales primarily for his philosophical ideas and cosmological thesis, he was also a noted mathematician and businessman. He traveled widely around the eastern Mediterranean and even visited Egypt where he learned geometry he later brought back to Greece. He also possessed a good understanding of astronomy, which included him predicting an eclipse of the sun in 585 BCE. It remains a mystery how Thales managed to predict the eclipse, which modern astronomy confirms to have occurred at the time he was said to have made the prediction. While in Egypt, Thales is said to have measured the height of the Great Pyramids via their shadows and could calculate the distance ships were from the ocean shore. He also theorized the Earth’s shape, size, and support, while also attempting to discover the size of the sun and the moon, and the cause of earthquakes. There is a legend speaking of how immensely fixated Thales was with studying the heavenly bodies that he fell into a well.