I think there are two question at play in whether or not Mr. Carson can be considered a scientist.
- Is the field in which Mr. Carson practiced a science?
- Is the work that Mr. Carson performed in this field scientific?
The answer to the first question is not as definitive as some might believe. Even among physicians, some view medicine as more art than science (every patient is different, not all treatments can be universally applied, have to tailor care to the individual, etc, etc). It sounds to me like you believe it falls into the realm of applied science, and since it incorporates the application of several branches of biological science, "applied science" is a logical and fitting tag.
The answer to the second question in my opinion should be handled with care, and not treated as a blanket answer for all medical physicians. So let's just take Mr. Carson's body of work and see if it fits the mold for "scientific." To me, the high level basic test of whether or not a study is scientific is whether or not it uses the scientific method. To remind everyone:
- Ask a question
- Do research
- Form a hypothesis
- Test the hypothesis with an experiment
- Analyze the data and form a conclusion
- Share your results
Just reading his Wikipedia article, the following jumped out at me:
I was talking to a friend of mine, who was a cardiothoracic surgeon, who was the chief of the division, and I said, "You guys operate on the heart in babies, how do you keep them from exsanguinating" and he says, "Well, we put them in hypothermic arrest." I said, "Is there any reason that -- if we were doing a set of Siamese twins that were joined at the head -- that we couldn't put them into hypothermic arrest, at the appropriate time, when we're likely to lose a lot of blood?" and he said, "No." I said, "Wow, this is great." Then I said, "Why am I putting my time into this? I'm not going to see any Siamese twins." So I kind of forgot about it, and lo and behold, two months later, along came these doctors from Germany, presenting this case of Siamese twins. And, I was asked for my opinion, and I then began to explain the techniques that should be used, and how we would incorporate hypothermic arrest, and everybody said "Wow! That sounds like it might work." And, my colleagues and I, a few of us went over to Germany. We looked at the twins. We actually put in scalp expanders, and five months later we brought them over and did the operation, and lo and behold, it worked.
Just from this blurb I can see that he formulates questions for a field of applied science, forms a hypothesis based on known science, and performs his experiments. Based on his published works, I think it's reasonably safe to assume that he analyzes results and shares the findings.
My opinion is that a doctor that does not simply read from a script of "How To Treat" is absolutely a scientist. The body is their Petri dish, so to speak. He shares his results, and I don't see anything about him being a kook, charlatan, or fraud, so I am assuming, given his prominence, that his results have been reproduced by others in the field. The human brain in particular is an area where medical science's understanding is pretty limited, so I think the tag is even more fitting for someone like Mr. Carson whose work didn't have a definitive How-To guide. However, your views may differ based on how you would answer the questions above.