Manuscript of Al Razi's writing (from 1094 AD)
Al Razi was born in Iran, in the Samanid kingdom, in 865 AD, when Iran was part of the Abbasid Empire. The Samanids were traders who encouraged education and the arts, and many scientists and artists lived in their kingdom. Al Razi seems to have started out as a musician, maybe playing the lute, before deciding to study chemistry. Al Razi studied chemistry to try to find a way to turn copper or lead into gold. He didn't manage to turn copper into gold (which is impossible), but he did make other chemical discoveries along the way. He invented methods of distillation and extraction to purify chemicals.
When Al Razi was middle-aged, maybe about 35 or 40 years old, he started to have problems with his eyes, possibly cataracts or damage from his chemistry experiments. He began to learn medicine in order to try to figure out what was wrong with his eyes. Al Razi studied medicine under Al Tabari, a well known doctor in the area.
Al Razi never did figure out what was wrong with his eyes. But he became a very good doctor. As a medical researcher, Al Razi was the first to distinguish smallpox and measles, though he thought they might be different stages or aspects of the same disease. Al Razi was also the first doctor to reject Greek ideas about humors and recognize that fever is not an illness in itself, but a way for your body to fight off an illness. He warned people not to expect cures for all diseases, and not to buy dangerous medicines from fake doctors who promised miracles. He was also very skeptical about religion and religious cures. Like his teacher, al Tabari, al Razi was very much interested in children's medicine. He was the first doctor to write a special medical book about children's diseases. He used opium as an anaesthetic during surgery.
After Al Razi's death, a Jewish doctor translated his writings on medicine into Latin, so that European doctors could read them. Al Razi became famous even as far away as Europe, where people called him "Rhazes".