"I swear by ApolloA US space programme which ran from 1961 to 1972 and took 12 astronauts to the moon and the ancient Greek god of the sun, poetry, and archery. the physician," the young, newly qualified doctor began as his parents looked proudly on. His oath included the promise that, "Into whatever houses I enter, I will go into them for the benefit of the sick, and will abstain from every voluntary act of mischief"; and that whatever he learnt about his patients, "I will not divulgeMake public. It comes from the Latin word "vulgus", meaning the common people., as reckoning that all such should be kept secret."

The oath he swore more than two millennia ago is still used, in a modified form, by doctors today. Known as the Hippocratic oath, it establishes the ethical basis on which they should work. But many other aspects of medicine are also attributed to the man who gave the oath his name.

Hippocrates was born on the Greek island of Kos at a time when illnesses were thought to result from the gods' displeasure. The surest way of recovering, therefore, was to consult a priest and find a way of appeasingSoothing their anger. Politicians who advocated giving in to Hitler's demands before the Second World War instead of fighting him were known as "appeasers". them.

Such doctors as there were devoted themselves to Asclepius, the god of healing. They believed that the body was a collection of isolated parts that should be treated individually, and the cures they administered relied entirely on what their patients told them about their symptoms.

Hippocrates turned all this on its head. Despite the mention of Apollo in the Hippocratic oath, his approach to sickness had nothing to do with the gods. He wrote of epilepsy - known as "the sacred disease" because of its dramatic symptoms - that, "Men believe that it is a divine disease only because of their ignorance and amazement."

The doctor's role, he argued, was to assist the healing power of nature. The body's inherent resistance to disease could be built up by means of a careful diet, gymnastics, rest, exercise, massage and bathing in the sea.

He insisted, moreover, that the human body must be treated as a single organism or "physis", in which the health of one part depended on all the others. And rather than just listening to what the patient said, a doctor should diagnose a disease by careful observation - noting how it progressed from one day to another and comparing one case with another, so that its outcome could be anticipated.

He devised different categories for illnesses, such as chronic and acute, and introduced terms including convalescence. He also emphasised the importance of mental health, regarding depression, delusions and panic attacks as symptoms of disease.

Since the dissection of bodies was forbidden by the Greeks, his knowledge of anatomy and surgery was limited. Nevertheless, he established surgical techniques for treating dislocated hips and jaws which were not improved upon until the 19th century.

Traditionally, Hippocrates was thought to have been born in around 470 BC. But a new book by Robin Lane Fox called The Invention of Medicine argues that he was born decades earlier, and was already writing influential works by then.

Some say, yes: Hippocrates was the first physician to approach ailments in a rational and systematic way, discounting the possibility of divine intervention. By devising a method of classifying diseases, he made it much easier to diagnose and treat them. He virtually invented the disciplines of aetiology and pathologyThe study of the behaviour of a disease, particularly by examining body tissues in a laboratory. Crime dramas often feature pathologists dissecting the bodies of murder victims., and the Hippocratic oath remains the cornerstone of medical ethics.

Others argue that scientific advances have changed medicine so much that it makes no sense to describe Hippocrates as modern. Much of his thinking was based on the theory put forward by Pythagoras that the body consisted of four fluids or 'humours' - black bileA fluid secreted in the liver and gallbladder to assist digestion. It can also mean bad temper or irritability., yellow bile, phlegmThe thick liquid that comes out of your throat when you have a wet cough. In Pythagoras's terms it was a fluid that caused laziness and indifference; to be "phlegmatic" is to have those characteristics. and blood - which needed to be balanced. Nobody thinks like that today.