alt Hacker NewsI doubt your conclusion that unified action needs unified mentation. One may take unified action without achieving unity of the contents of the brain. Acting with instantaneous regret if you will, flying by the seat of your pants, etc. The brain seems to be able to let competing subsystems alternate getting expressed in action.
Not all brain activity is unified, I just claim it must unify on the output side - behavior and language.
But this is not a brain or organism only problem. Even a cell must unify in crucial moments such as division and chemotaxis. A cell either divides or not, no mid point. To persist it must unify at some moments in its activity, yet it is a distributed system of many parts.
The core principle here is - what is the unit of selection? the cell survives or not as a whole, the organism also survives or not as a whole, not organ by organ. Selection chooses the mechanisms that are viable.