Are all these theories concrete? Explain. Why do you think the social sciences incorporate disciplines such as religion, geography, history, sociology, psychology and economics? How do these institutions overlap as a social science?
No. all these theories may not be necessarily concrete because social science is about the human behaviors and thinking.
Social sciences incorporate its disciplines because these are all about the human society. And there is an overlapping because there are similarities, such as between religion and history or geography. Though people may have different cultures with respect to their races, but still similarities could still be pointed out.
In the fields of economics, these has something to do with how people uses their money or financial management and the degree of their spending may vary but this must be already situational and personal and has nothing to do with the theories of economics.
If all these theories cannot be concrete it is because people will always find better ways to make their life better, we are always learning from our day to day experiences as a people. The fields of social science though very much similar to each other will just differ in how people reacts and relates with each other, because all us cannot be the same, as an individual we are unique. Different cultures may exist but does not separate us from each other as a people. We may have different kind of religion but we do still believe in one God.