We tend to think of the words doctor and physician as synonymous, although that is not quite true. There are subtle differences between those words, as well as the word surgeon.
While reading Joshua Kendall's The Man Who Made Lists, a biography of Peter Mark Roget, the man responsible for Roget's Thesaurus, I learned that the difference between doctors and physicians was even more important in the late 18th century than it is today. Roget received sufficient medical training to become a physician, not just a doctor. "In the late 1700s," Kendall writes, "physicians, who were the only doctors to receive extensive university training, constituted a small elite - just ten percent of all doctors."
Surgeons were in another classification altogether. "While physicians treated internal diseases (say, a fever), surgeons treated exclusively external disorders (say, a broken bone)," Kendall says. "Considered technicians rather than men of science, surgeons were addressed as 'Mister' rather than 'Doctor' -- a custom that continues to this day throughout the United Kingdom." Remember that at one time surgeons and barbers were regarded as one and the same thing, the red in the barber's pole representing blood.
Here's how the American Heritage Dictionary, fourth edition, defines physician, doctor and surgeon:
physician - 1. A person licensed to practice medicine; a medical doctor. 2. A person who practices general medicine as distinct from a surgeon.
doctor - 1. A person, especially a physician, dentist, or veterinarian, trained in the healing arts and licensed to practice. 2. A person who has earned the highest academic degree awarded by a college or university in a specified discipline.
surgeon - 1. A physician specializing in surgery.
Thus, all physicians are doctors and all surgeons are physicians, but not all doctors are physicians and not all physicians are surgeons.
When I worked as a newspaper copy editor, our style allowed only medical doctors to be given a Dr. before their names. The thinking was that because most readers associated that title with physicians, it would be misleading to refer to ministers or college professors as doctors. This always struck me as a little unfair to those men and women who had earned their doctorates in fields other than medicine, as well as underestimating the intelligence of our readers.