There cannot be a final theory in principle. We have the (local) universe. Explanation? Explaining the universe means, first, assuming the existence of some transcendent field that contains it. For example, the (local) universe is just a bubble inside the Multiverse, which is a churning vastness that births universes like Brahma breathing. That is, we understand the universe by placing our perspective external to it. We assume the field of the Multiverse that transcends but contains the universe. Getting-at and under-standing contain this idea: to explain is to own, to own is to generate, and generation is from an explanandum-transcendent space, where transcendence comes either from (1) greater extension or (2) higher dimensionality. We grasp the meaning of line from space or a plane. That is, our act of understanding begins by identifying awareness with a vast stuff from which the explanandum is to be cut and thereby generated.
Explaining the universe assumes the Multiverse, and this in turn is the next thing to be explained. To do that, we must assume something else “more basic” and “less presumptive.” We will inevitably start digging into the stuff that is really a priori true about all object uberhaupt, which is the cognitive formalisms we depend on in order to have objects that are illuminations of consciousness. Forms that are innate to fact perception are forms holding of all facts.
So the more-basic fact that transcends and contains the Multiverse will be some metaphysical principles underlying the formalism we use to perform our empirically validated operations. These are generally of the form: being has quality F at location S at time T. The Multiverse is explained, then, as a consequence of deep principles that determine operations in a formalism.
And what explains our attraction to these principles, such as conservation laws and symmetry? We see that our answer must make the explanans even more implicated in cognition and less in F, S, and T. The Ultimate Reality is turning out to be reason itself, as Kant and Hegel worked out.
That’s the first sad part about explanation: it gets farther from the object and closer to the subject. The second part is this: every explanandum that has content must have a sufficient reason, which means that every explanandum is an explanans. Every answer that makes sense makes sense—i.e., it is being generated from a transcendent presumption.
From this I infer that there is no final truth or theory of everything because that theory itself must then also be what is explained. Why is reality that way? Because p? But why is it the case that p? Because q? If we understand the theory, we have to ask: what explains the fact that that theory (and no other) is true? No answer is forthcoming, other than “because our reason only works in certain ways.”