"Perfect" is one of these concepts. How can anyone identify when anything has reached perfection? That is the thesis of the book and movie The Black Swan. In the plot the protagonist did it by killing herself--not many people's way of thinking about being "perfect".
There is much more say and, likely, I will discuss the concept of a silly concept this further in future posts. I know I will discuss many examples from the socio-cultural/political/economic/historic/geographic discipline in posts in the near future. Some of these will strike at the foundations of some political theories, yet if the reader thinks about it, they will find that they are silly concepts, based on the definition above.