The theory of everything is often thought to be carried out in the field of physics. This makes good sense so far as physics indeed investigates the fundamental principles of how the world works. But why should a theory of everything be made up of formulas and physical principles?
I am suggesting that theories of everything could be carried out in multiple levels of scientific research. It is often discussed which branch of science is the most fundamental. Is it physics? Is it philosophy? Or maybe it is the neuropsychologists that are on the right track? There are so many places to start an investigation of the world.
The human condition is that we necessarily take in the world through our senses, and we are therefor (some would say) confined to these experiences. We have a fairly good idea of how to use our senses, but if someone were to state that our mind holds knowledge, that can be reached without the use of our normally defined five senses (the yoga traditions actually does this when teaching us about the ‘cit-acash’ (mind-space (with a dozen other possible translations!)) which holds all information in the universe and can be reached though meditation), then all we can say against it is that our current evidence does not point in that direction. There is not a bulletproof way to dismiss it though (just think of Karl Popper, and how in is older days, he realized the problems of the falsification principle after having scorned the verificationists!).
My point is that we have many ways to come to an understanding of the world we live in, and it seems to me that a descriptions in different fields will make up a series of stories that together can show us what the world is like. To then try and integrate all of these would be the ideal way to make a theory, but is this possible? The differentiation happened throughout history. The people in ancient Greece were philosophizing and exploring the world in various fashions.
Now – what kind of science is needed to weave together all of these threads again? Either we go back to philosophy or we create a new modern philosophy, that can cope with the enormous amounts of information, that has been gathered since humans started wondering about life. But what exactly will that be like?