Campbell's theory could be considered the Grand Unifying Theory but he chose to call it My Big TOE (Theory Of Everything). Consciousness gave rise to brains not the other way round. The entire physical universe, all the quantum effects, and relativity, are a simulation. This sounds crazy at first but even the double split experiment provides convincing evidence that the universe is information-based not material-based.
Now if the universe is computed then where is the computer? It can only reside completely outside of and separate from the universe itself. (The universe cannot compute itself). The difficulty many physicists have with the hard problem of consciousness is they are still looking inside the universe for answers.
Campbell's trilogy 'My Big T.O.E.' is on amazon or for free at google books https://books.google.com/books?id=RYHtBPiZVgsC&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false
edit: I watched his 2011 Calgary presentation on youtube first and that was enough to get me to read the trilogy.