In fact this happens with any form of social or psychological science. If you start with, anything is a spectrum, gray zone, nuance... you are not able to make

In fact this happens with any form of social or psychological science. If you start with, anything is a spectrum, gray zone, nuance... you are not able to make different categories. Even with music, pop, rock, metal, hiphop, balade,... if you ask any musician they will tell their music dies not fit any category. My point is, making categories is just a starting point for certain sorts of science and literature.