Definitely pure theory, of a very abstract variety. But that being said, don't devalue gauge/gravity holography too quickly. Holographic arguments can be used

Definitely pure theory, of a very abstract variety. But that being said, don't devalue gauge/gravity holography too quickly. Holographic arguments can be used to connect physical theories pretty similar to known, measurable particle physics to a gravitational/stringy theory (not a "theory of everything" variant, mind you) where some results are easier to calculate. Those methods are actually within spitting distance of being experimentally relevant today. (But even if these methods were to give an experimental prediction that was confirmed at RHIC or the LHC or somewhere, it would only be evidence supporting the math of string theory. It wouldn't be directly related to whether string theory is a correct theory of quantum gravity.)