The Evolution explains the origins and the function of the nervous system.
In the pre- NS world, the interplay between the environment and the organism determines the survival. With increased complexity of the organism, the repertoire of the adaptive reactions increased both in spatial and in the temporal realms.
In pre-NS world the changes of the environment and organisms adaptive reactions are random.
To relate these environment’s changes to organism’s action you need the behavior.
The behavior includes the information about the environment’s changes (the niche) the ways to remember them , the organism’s action and the way to remember it. Intent/ reward system is also included very early. The evolutionary benefits of processing and of organizing these data, “ pushed” the development of the nervous system.
So, as I understand this, the content of the organism’s nervous system are these information pieces or neural networks organised in systems being actually behaviors. This is organism’s Universe with the intent/reward system unifying them into an agent, (in more complex organisms, it become “I” or consciousness).
These Universes overlap , as the experiences overlap, depending on the complexity and socialization of the organism. This is so simple , especially comparing to the Quantum- everything world. Well, with the Human World it is slightly more complicated , as we are v.v. complex and v.v. hypersocial- so we created from those overlapping experiences a “Nobody’s Universe”, we call real.
I do not believe such a thing exists. Any animal’s Universe is perfectly real, and My Universe is real. Animal’s do not have any need to burden their nervous system with Nobody’s Universe, the evolutionary process would not allow for it, and I can’t think how the humans could have grown one. Instead of Subjective vs Objective World, I have one, real My World, with some things more personal , not overlapping much, others- heavily overlapped.