Im reading 'three roads to quantum gravity', and it's written there that any theory trying to unify between QM and GR has as conclusion that space has a discrete quantity where you cannot divide space more than this. now how would you propose to verify this assertion? I mean assume you've divide space up to the planck scale 10^-33m, why would this opertaion would stop there, what would stop us from dividing space even more than that? and how would we know for sure that we cannot divide it even more than that? thanks in advance.