Its non-
literal meaning is the area of
thought or
opinion in between the two
absolutes of
right and
wrong or
good and
bad.
Normals,
mundanes,
induhviduals,
fundamentalists, and
religious fanatics are all
people who tend to choose one of the two absolutes and
pretend that the
shades of
grey don't exist. This tends to hamper their
mental growth while giving them an
excuse to try and
force everyone else to either choose the good or right thing, or
automatically be
bad or
wrong.