What makes a social science a science?
The social sciences are Anthropology, Sociology, Psychology, and various sub-fields of Geography. Economics, and political science fill out the list. I mention them separately as Economics has a spot on the Nobel Prize list, and political science is the least scientific, and had "science" in its name.
There should be no question that the first mentioned study areas are sciences; they make direct observation, conduct experiments and repeated time series study. For the other two I refer to the Nobel committee.
While I am sure some will disagree with me, I believe that science is best defined by the methods rather than the subject. If the subject is studied through the application of the scientific method; constructing a hypotheses, defining a repeatable experimental procedure, collecting experimental data, and analyzing the data to validate or disprove the hypothesis, then it can be consider a science. The key is ensuring that the experiment is repeatable and that the conclusion is data based.
So yes; based upon my definition Social Science can be a science.
I have come to this definition of ‘science' as an engineer turned business Process Consultant. Early in my career I would have been much more closed minded regarding what constitutes a science. However, the more I worked in the corporate world the more I realized that while the theories are different the application of the scientific method can be used to investigate everything from industrial catalyst reactor yields to market segmentation behavior. A well constructed hypothesis and a means of collecting good experimental data can be used to generalize any process whether it's a natural science, a business process, or social network behavior. This is what process improvement methodologies like Six Sigma are based upon and why business consultants can succeed in industries/issues where they have little direct experience.
Science is the collection of knowledge gained from controlled and reproducable experiments, and theories based on those experiments. As long as experiments in social science are testable and reproducable, their ideas is a science.