In the ancient world the gods controlled, and thus were responsible for, everything that happened. This worldview went unquestioned until Thales of Miletus started searching for rational rather than supernatural explanations for the way the world worked. His thinking was followed up by a stream of great thinkers who speculated that the world was governed by a single substance. This school of thought then expanded to suggest that, aside from the known earth, water, wind and fire, there were many elements at play that made up the world and, by the early 5th century BC, the concept of tiny particles called atoms was first presented.
