You may want to move this to the discussion board.
For me, the people who have changed the framework through which we view science are the key people. There are several that come to mind...
Darwin, evolution by means of natural selection.
Newton, laws of motion.
Mendeleev, devising the Periodic Table.
And for medical doctors, Pasteur, germ theory of disease.
These people changed the way things that were already known were viewed and applied, as well as enabled further discoveries in their fields. There have been many who made extraordinary discoveries, but these people changed how we looked at those discoveries. Just imagine if we still thought disease was still caused by evil spirits.
By doctors, do you mean M.D. or PhD, or both? All PhD scientists are "doctors," but not necessarily medical doctors.
Michael H. Hart's book The 100: A Ranking of the Most Influential Persons in History lists the top 5 scientists as:
- Newton (2nd all-time)
- Einstein (10th)
- Pasteur (11th)
- Darwin (16th)
- Copernicus (19th)
Of the doctors/biologists, he ranks them as such:
- Van Leewenhoek (microscopic life)
- Morton (anesthesiology)
- Fleming (penicilin)
- Harvey (blood circulation)
- Mendel (genetics)
There have been so many great scientists and doctors that it would be very hard to single one out. There also many different fields of medicine and science in which discoveries have been made. Then there is the historical aspect to consider, many of the greatest scientists lived in different time periods and societies. For example the Romans, Egyptians and Mayans were all known for there brilliance in science. If I had to name one man, though not officially a doctor but known for his work on human anatomy and his scientific work among other interests it would be Leonardo da Vinci.
One of the greatest doctors and scientists of all time is Jonas Salk. While he is arguably the greatest, there have been many others that have not touched the lives of ordinary people in the way that he did. Polio was the most debilitating disease affecting post-War America. Jonas Salk's immunization vaccine has led to almost complete eradicationof the disease. Only smallpox has been complete eradicated, and if polio became the other, Jonas Salk would no doubt go down in history as one of the greatest doctors who completely stopped 400,000 people from contracting the disease every year.