How does One Flew Over the Cuckoo's Nest position the reader to reconsider what is sane?

The vast majority of Kesey's novel takes place in a mental
institution, of course, and for some characters, that seems an appropriate place for
them, as many have serious mental issues.  But mental health care in general and in
Nurse Ratched's ward in particular, electroshock therapy, heavy sedation, lobotomies and
control through fear and humiliation are the order of the day, and it doesn't take long
before the reader sides with McMurphy and company.  Such was typical of institutions in
the 1950s when the story takes place.

So ask yourself the
question, how does society define what is sane and insane?  And was it sane to treat the
patients to such harsh and demeaning conditions?  What if McMurphy is sane (OK, and a
little eccentric, but sane)?

At the end of the story we
find that Chief has been sane all along, perhaps the most sane observer in the entire
place, and so Kesey perfectly positions us to question our thinking about
sanity.