The role of impossibility...‏

Universes that are complex enough
to give rise to consciousness
impose limits on what can be known
about them from within.
 
There is more to impossibility
than first meets the eye,
its role in our understanding
of things is far from negative.
 
We will gradually come to appreciate
that the things that cannot be known,
that cannot be done, and cannot be seen,
define our Universe more clearly,
more completely, and more sharply
than those that can.
 
John D. Barrow