Thanks for responding! I never meant to claim that I am right. The whole purpose I am engaged in here is that I do not understand the proof at all and am trying to understand it better.

Here is where F_QG is introduced in the proof:

As we do not have a fully consistent theory of quantum gravity, several different axiomatic systems have been proposed to model quantum gravity [26–32]. In all these programs, it is assumed a candidate theory of quantum gravity is encoded as a computational formal system FQG = {LQG, ΣQG, Ralg}

Here, LQG a first-order language whose non-logical symbols denote quantum states, fields, curvature, causal relations, etc. ΣQG = {A1, A2, . . . } is a finite (or at least recursively- enumerable) set of closed LQG-sentences embodying the fundamental physical principles. Ralg the standard, effective rules of inference used for computations

Is this not just saying that it is the existing theories (string theory, LQG, etc.) that are assuming gravity takes the form of a formal computational system? And so, F_QG as it is defined above is how any formal computational system is logically constructed, as in it has to have those three components in order to logically be a formal computational system?

I am not a logician and do not understand what a first-order language is, or closed sentences or all those logic terms in the definition of notation. However, is F_QG in this case not just logically how any theory would need to be constructed in order to logically be a formal computational system? Is there an assumption being made here with regard to those three components in how formal systems are logically constructed?