ANNOTATION:
Self-consistency for both Humans and the Earth

During the day one absorbs information.  This inevitably forms 
inconsistencies with what one already knows.  During sleep the 
brain forms a self-consistent system incorporating the new 
data.  This refined belief system takes up less space than the 
 previous inconsistent system, so the remaining space is 
released.  Dreams are the byproduct of all this, an emergent 
phenomenon.
The entire Earth is in the process of forming a self-consistent 
system.  Achieving this would literally mean that there are no 
more problems to solve.  However, we take in data from outside 
the Earth through astronomy, so we will never settle down to 
self-consistency.  There will always be frontiers to conquer. 
And once we begin to communicate with other stellar systems we 
will have to accommodate their knowledge too, so we shall 
never have to worry about becoming static and ossified.

        

REPLY: Possible Theory on Learning during Dreams

Perhaps a good model for what happens to us during sleep and 
dreaming is that the mind undergoes constructivist learning 
using concepts acquired during the day.   Concepts are 
experimentally used as building blocks to create metaconcepts.  
Some of these are useful and retained, some are not.  Some may 
be ill-formed and bizarre.  According to constructivist 
principles these would be returned to the "supply bin" of 
concepts, and these would be the stuff dreams are made of, 
explaining their illogical and bizarre features.  At least this 
is what I come up with through introspection.