And then there was Karl Popper. He said that the hallmark of scientific theories is that these are falsifiable. You can prove them wrong by empirical evidence. A theory that is not amenable to falsification is not a scientific theory. Thus he gave a method for demarcation of scientific and non-scientific theories. This is the Popperian wisdom. Then once a journalist of science called John Horgan once interviewed Popper for Scientific American. Is your theory ( of demarcation of scientific theories) falsifiable? Popper leaned forward and put his hand on Horgan's hand and said, "I do not want to hurt you - that is a silly question - my theory is not a theory of science". Cute.