Most Greeks thought that dissecting dead bodies was wrong but it was through dissection that the most important discoveries about the body were made. One of the first doctors to carry out dissections was Herophilus who lived around 250 BC. His most important discovery was that the brain controls the body. Another great doctor working in Alexandria was Erasistratus who almost made an equally important discovery. Whilst dissecting a human heart, Erasistratus noticed it had four one-way valves.
He wondered why and finally decided the heart was some kind of pump. But he wasnt well liked partly because he was one of the only Greek doctors who didnt believe in the theory of the four humours and so unfortunately his ideas were never developed. Although 1800 years later, he was proved to be correct and the heart was proven to pump blood around the body. However, although these doctors made many discoveries about natural causes of illness, many did not stop believing in the supernatural on the whole and in fact in the Hippocratic oath written by Hippocrates, a doctor must swear by Apollo, Asclepios and all the Gods. And many average Greeks never stopped believing that the Gods were the causes and curers of illness. If a person was sick, they usually went to an Asclepios where Asclepios, the god of healing, cured them while they were sleeping.
Many stories were recorded where the patient had awoken to find themselves surrounded in blood and were then healed, and most civilians believed the Gods to be a more reliable source of healing than the doctors. I think that most Greeks did not change their opinions on healing because, similarly to our modern day selves, they did not like the idea of change and in fact feared it. They were happy believing in the Gods and therefore found it difficult to accept that their beliefs may not have been the best way to look after them. Outside of medicine however, most Greeks believed in the supernatural and even thought thunder and lightning to be the cause of the Gods. I think that the role of the Gods in Ancient Greece was incredibly important to the same extent as Catholicism in mediaeval Britain, and Judaism in the biblical Middle East. They were the religion and culture of the Greeks and ancient Greek life revolved around them.
Therefore it must have been difficult for traditional Greeks to understand that there was one aspect of their lives which the Gods had no control over and for this reason I believe many Greeks continued to depend on the supernatural long after natural causes and cures were developed. However I also believe that the Greek philosophers and doctors played a tremendously large part in the development of medicine, particularly Hippocrates and Herophilus who made such great discoveries and developments that centuries of medical theories depended on them. I think that in general, its researchers and doctors who made important and extensive changes in the history of medicine represent Greek medicine. I also think it is fair to say that in medicine, Greek civilians were far less dependant on the supernatural than in any other aspect of their lives and therefore I can conclude that the Greeks made an incredible amount of contributions to the development of medicine and that in most cases they no longer believed in the supernatural as a cause and cure of illness.