Classical discoveries: Some humans begin to suspect the existence of laws of nature

Signs of a distinctive, new and eccentric pattern of human behaviour began to occur in what became the most famous of all the Greek city states – Athens. Long before the Persians razed the city to the ground in 480BCE this city had become a laboratory for experiments in novel human behaviour. In c594BCE, a poet called Solon won a victory for the city by capturing the nearby island of Salamis. He used the considerable power and prestige gained from this triumph to seize political control.

His reforms involved redistributing political power so that it wasn't just the most powerful families who participated in politics and the judicial system. He created a setup that can now be seen as the first attempt to create a democratic government. Nobles remained the city's magistrates, but Solon introduced juries into most social disputes, and so, for the first time, involved ordinary citizens in the deliberations of justice.

Part of the reason these people could afford to spend so much time in political and judicial deliberation was thanks to the highly nutritious olives that grew in groves that tumbled down to the Mediterranean shores. Because they were so easy to grow, preserve, transport and trade, these fruits afforded Greek people riches in the form of spare time with which to experiment with new ways of life and observing how the natural world works.

At just about the same time, the beginnings of what was soon to become a revolution in scientific and religious thought was emerging just across the narrow stretch of sea separating Europe from Asia – the Bosphorus.

Miletus, on the west coast of Turkey, was home to a man called Thales (born c640BCE), who became famous for correctly predicting that a solar eclipse would take place in the afternoon of 28 May 585BCE. Thales demonstrated that the movements of the planets could be predicted using a set of astronomical tables originally compiled by holy men in Babylon and Egypt. The invasions of Darius had brought such knowledge, stored on clay tablets, into western Turkey. When these fell into the hands of someone like Thales, with a keen eye for numbers and mathematics, patterns began to emerge that could then be extrapolated to predict events such as a solar eclipse. Anyone who could make an accurate prediction of something as dramatic as a solar eclipse was bound to make quite a stir in a world where such events were traditionally believed to be caused by the arbitrary whims of all-powerful gods. Thales' reputation spread fast and far.

The discovery of a set of rules that governed the movement of the planets in the heavens also caused some people to wonder what else in nature worked on similarly predictable lines. Thales' lifelong quest for a set of universal laws to explain nature was taken up by other philosophers, many of whom lived in Athens. Socrates (470BCE–399BCE) was a famous Athenian philosopher who also believed in a set of natural universal laws. Like Buddha ( see Part 7), Socrates thought that a man's soul could be improved over time but not through mastering stillness of the mind – rather, by the opposite. For Socrates the path to enlightenment involved the application of problem-solving reason, high-powered discussion and heated debate.

By about 460BCE, debate, argument, rhetoric and oratory had become the chief virtues of civic life in Athenian society. For Socrates, these skills were at the core of his philosophical method. Nothing that he actually wrote has survived, but we know a great deal about him and his ideas thanks to his pupil Plato who also became one of the most influential philosophers of all time.

Plato's most famous philosophical work, The Republic, features a debate about the best way to rule a human society. Plato also believed that what underpinned the universe was a reality that didn't originate from the traditional ragbag of Greek gods like Zeus, Apollo and Aphrodite who inflicted their fancies on an unsuspecting world. Instead, Plato believed that the truth could be revealed through philosophical reasoning and contemplation. Therefore, in his description of an ideal society, it was philosopher-kings who ruled society sharing the wisdom of their insights with their subjects.