Science is our body of knowledge of the natural world. It is more than just a long list of facts: it includes the theories that fit the facts together and explain them. Facts tell us what is so, theories tell us why it is so.
Science used to be called natural philosophy because it was the branch of philosophy that explained the natural world. But no one calls it that now because science no longer works the way philosophy does. It has become something halfway between philosophy and geometry.
These days science almost always means Western science. There were other sciences: Greek science, Arab science, Chinese science and so on.
Western science is built on Greek science but it takes it much further. What distinguishes the two are the rules that they follow.
Science is not just theories and facts: it is also a set of rules about how to do science.
Greek science had three rules:
- Observation: gather the facts.
- Theory: apply reason to the facts to come up with a theory that explains them.
- You may use no gods in your theory.
Before the Greeks everyone explained nature by gods and spirits. The Greeks, however, starting with Thales, attempted to explain nature as a system that kept on going without help from the gods. Gods may have created nature and may act within it, but they do not keep it in operation. It goes on by itself.
Because gods can explain everything, they explain nothing. Also, god theory gives man no means to control nature by himself. It does not lead to invention, but to prayer and sacrifice.
As good as it was, Greek science had a weakness: There was no way to prove a theory right or wrong so long as it kept within the bounds of fact and reason, which any serious theory did. The choice between theories became a matter of taste. Science was divided into schools of thought just like the philosophy from which it sprang.
To mend this Western science added two new rules:
- Occam’s razor: the simplest theory that explains the most facts is the best.
- Experiment: A theory must have a test, often called an experiment, by which it can be proved false.
A good theory will not only explain the known facts but also predict something surprising, a previously unknown fact. If it turns out to be false, the theory is rejected. If it turns out to be true, it will gain followers, win awards and in time be written up in school books as the truth.
The great age of Greek science ran from the time of Thales, about 600 BC, till about 200 AD. By then most of what could be done in Greek science had already had been done. The Arabs were able to take it a bit further, but that was all.
It was not till the time of Galileo, about 1600, with the rise of Western science that another great age of science came. We live in that age.