advantage of string theory over other theory-of-everything candidates

Question

I am getting curious over why string theory, especially M-theory, is the most popular candidate for the theory of everything.

It seems that all candidates of the theory of everything lack substantial experimental supports, so why is string theory so special?

Thanks.

Answer 1

String theory is currently the only even remotely viable theory of everything.

There are various other approaches to quantum gravity like Loop Quantum Gravity and Causal Dynamical Triangulation (possibly Causal Sets as well), but these are specific to gravity and make no attempt to, for example, include the Standard Model. While these theories attempt to describe gravity, String/M theory is the only approach that describes all four forces in one theory.