I watched Shutter Island last night. Firstly absolutely brilliant movie.

So my question... was he a nutter or not?

I feel that he was due to you never seeing him on the mainland, the opening sequence was of him on the ferry with his "new" partner.
The spooky looking bird as he walked in had her finger over her mouth as to say that she was told to keep quiet.
If they were conducting such horrific experiments in the lighthouse, and all of the staff knew, the public would have known.
And finally, after all the shit the poor bloke had gone through. e.g Concentration camps and what his crazy bitch wife did, most people would definitely be damaged goods after that.

What are your thoughts? Oh and if you haven't watched it... WATCH IT!!

P.S What did the note mean? I know the 67 part, but the law of 4 line?