ABSTRACT
However, practising scientists usually would not label these as theories. They tend to reserve that honorific term for items such as Newton's theory of gravitation, Young and Fresnel's wave theory of light, the kinetic theory of heat and Einstein's theory of relativity. What is the main difference between the two? Complexity does play a role, but not an essential one. The difference lies in that members of the latter group bring with them new concepts. They introduce new perspectives - new ways of looking at reality. In short, they are new conceptions. In the last chapter, we labelled them 'real-nature theories', which is not exactly appropriate. Let us, from now on, call them conceptual theories.2
