If we're going to say that only scientists are qualified to define what science is or things like " You are not a scientist, and your opinions on what is or is not a science are meaningless", it becomes important to understand just what defines whether one is a scientist.
Does having a Ph.D at an accredited university always mean that the bearer is a scientist and is thereby qualified to define what science is or give opinions on it?
Thanks,
-Jesse
To my way of thinking science is defined by following the scientific method.
Of course there are a lot of folks out there without Ph.D.s who are scientists, while some folks with Ph.D.s are not following the scientific method.
Anyone can give opinions on science, but ones level of education must be taken into account. My opinions on quantum theory should not be taken very seriously, even though I have a Ph.D. -- I know absolutely nothing about that field.
Now one problem arises when Ph.D.s, well qualified in one field, opine in another field. Expertise in one field does not necessarily extend to another field. Another problem arises when experts jump off the train and ignore the scientific method. We see this in some of the leading creationists. By accepting religion as the overriding source of "knowledge" in their lives they cease to follow the scientific method. They are no longer doing science, and their judgment is no longer to be trusted. Most folks take a middle ground and separate the beliefs of religion from the methods and results of science.
I have seen several articles on radiocarbon dating, one of my fields of study, which posit a need to recalibrate radiocarbon dates based on the effects of the global flood on carbon isotopes in the atmosphere. This is an example of religion overriding evidence. So far there is no evidence for a global flood, let alone that it seriously altered the carbon isotopes in the atmosphere. Folks who propose ideas like this are arguing from religious belief, hoping to twist the scientific evidence enough to somehow squeeze it into their required framework. The more twisting and bending that is required to make things fit the less reliability an idea has.
That is why the theory of evolution is considered to be such a strong theory. It could have been seriously damaged by the new field of genetics in the last 50-60 years, but it was supported instead. New findings have been fitting in quite well, with only very minor tweaking of the details. None of the finds since Darwin wrote 150 years ago have suggested that the overall structure of the theory of evolution is incorrect. That wholesale bending and twisting of evidence that is required to make, for example, the global flood fit the data, is not required for the theory of evolution.
So to summarize, scientists are those who follow the scientific method regardless of training or background.