What is Magic besides some form of superintelligence, or at least the remnants of superintelligence? The strongest evidence is that magic-users and even creators don't really have to understand how the spells actually work in order to use them. There is information entering the system from somewhere, and it's enough information to accurately interpret the vague wand movements and sounds of humans and do sufficiently amazing things without too many chaotic side-effects. Even the chaotic side-effects are usually improbably harmless. It's like an almost-Friendly, or perhaps a broken previously-Friendly, AI. Possibly the result of some ancient Singularity that is no longer explicitly remembered.