An eclipse of the moon. You can see the curved shadow of the Earth. Logic tells you the earth is round.

## Making predictions

Once people have seen that something happens through observation, sooner or later it will occur to them to ask why it happens. And is there any way to prove that it will happen the same way every time? Sumerians developed advanced math to predict the movements of the planets, for example. Thales figured out how to predict a solar eclipse.

## Doing experiments

The Egyptians, according to Herodotus, used experiments to see what would happen in a certain situation. For instance, Herodotus reports that the Pharaoh wanted to find out what the first language on earth was. So he ordered two babies to be put in a house alone. He ordered the slaves who took care of them not to speak at all, to see what the babies would say first naturally. Around the same time, in 1300 BC, the Indian astronomer Lagadha used geometry to write a book of rules for the movement of the sun and moon as they seemed to move around the earth.

### Who was Herodotus?Science and math in early India

Diagram for proving the Pythagorean Theorem

## Logical proofs

In the 500s BC, the Greek philosopher Pythagoras was interested in proving that things had to be true every time, rather than just observing that they were true most of the time. Then Socrates began to develop a way of thinking and speaking which would let you prove that a certain statement was or was not true. We call that logic. (Logic comes from the Greek word “logos”, a word, so it just means using words.) Socrates’ student Plato continued this idea. And Plato’s student Aristotle applied this logic to the natural world.

### Who was Pythagoras?Socrates the philosopherAristotle and nature

In the Hellenistic period, many Greek, African, and West Asian scientists like Euclid and Aristarchus used Aristotle’s logical system. With this system, they investigated mathematicsbiology, astronomy, and medicine.

### Euclid and geometryAristarchus and astronomyEgyptian medicine and doctorsIndian mathematicians

These studies took place especially in the great Library at Alexandria in Egypt. Egyptian scientists kept right on working after the Romans took over ruling Greece and Egypt. So in the Roman period, an African scientist named Ptolemy did careful experiments to figure out how people’s eyes worked. Meanwhile, Indian mathematicians were working out rules governing different infinities and probabilities.

Al Tusi‘s diagram of linear motion from circular motion

## The laws of motion

After the Islamic Empire was established in the late 600s AD, scientific research took off again. In physicsIbn Sina figured out the basic natural laws governing motion and momentum in the 900s AD. In the 1100s AD, Maimonides realized that people got sick from bad water and air (though he didn’t know about germs), rather than from magic spells or curses. Ibn Rushd, at the same time, tried to use logic to figure out the nature of the soul.

## Logic of love?

By the 1100s AD, Europe was for the first time becoming a center for scientific thought. Monks, in the role of professors, were teaching Socratic logic to students in the monastic schools and cathedral schools (the beginnings of modern universities) at Paris and Cambridge and Oxford. Men like Peter Abelard tried to use logic to prove the existence of God, and to define His nature. At the ducal court of Aquitaine, Eleanor of Aquitaine and her court used the same logical principles to discuss the nature of love.

## Religion and logical thought

By the 1200s, Islamic and European scholars talked to each other more. Thomas Aquinas and Roger Bacon imitated the work of MaimonidesIbn Sina and Ibn Rushd to build a more logical version of Christianity. In the next century – the 1300s AD – Ibn Khaldun in North Africa applied logical principles to the study of history and economics, breaking new ground.