Periodically one encounters the question of whether this or that topic or discipline is a science or not a science. This is a venerable problem that even has its own name (the demarcation problem) that I have written about extensively in the past (see my 2011 series of posts on the Logic of Science) and the consensus has been that it is impossible to specify both necessary and sufficient conditions that are necessary to do so. In most cases this inability to construct a strict demarcation rule does not really matter in any tangible way. After all, what does it matter what label you give something? But unfortunately it is the case that being considered ‘scientific’ adds a certain authority to statements, which is why people invoke it so frequently.
But even one can’t get complete demarcation criteria, one can usually specify just necessary conditions (such as being naturalistic, empirical, testable, predictive) that can at least identify what is not science if they do not meet those minimum criteria. It is just this question that is usually important anyway. So, we can say that creationism or intelligent design is not science while we cannot say that string theory is not science. In ambiguous cases, it is the collective judgment of the community of scientists that is the ultimate arbiter.
It is similar to art. I would argue that it is impossible to create demarcation criteria that determine what is art and what is not art, but we leave it up to the experts in the artistic community to make the final judgment, even if we may not agree with some of their conclusions.
Jon Brock argues that it is important that psychology be considered a science, while neuroskeptic says that asking “Is psychology science?” is to ask the wrong question and the problem is that scientific knowledge is being conflated with true knowledge, an idea that can be traced back to Aristotle.
I feel that while we cannot say that psychology is not a science, we cannot say that it is a science either. But as far as I can see, nothing really hinges on how one answers that question except for bureaucratic purposes in universities and funding agencies who need to know which box to put it in.