We are told that the definition of sanity is the ability to tell the difference between reality and fantasy. The crazy people out there who commit violent acts against innocent people truly believe their view of reality and if they are ever caught alive, feel no remorse and do not repent as they have decided in advance that their beliefs and fears are real.
Be that as it may; one is not permitted to act on those beliefs and murder people.
When it comes to deciding sanity in the dementia population our job is to keep the people safe and unable to harm themselves or others. Most of the residents in my husband's memory care facility are in that group who live most of the time within their own delusions-their own decisions about what is real and what is fantasy. Their knowledge of personal property and personal space is lost; their sense of control remains although they have only a very limited sphere of control over their everyday lives.
Not only are we unable to keep them sane, I am sure it is their personal interest not to do so.
What do I mean?
When he is rational, my husband states, "I don't know what to do," and he sits staring into space until he feels hungry, tired or has to use the bathroom. When he is animated, I find now that he is fantasizing about pieces of old concerns, record-keeping, passes, statements, banks and women. Much of his rambling is not understandable, only isolated words get produced in full, but he is content, full of dignity and purpose, rambling aloud in a soft spoken tone, probably to anyone who will listen, what is going on in his head, which has nothing to do with the reality of the moment. This time we were sitting on a bench feeding the ducks at the lake.
He is living his time in the US Army when he was stationed in Japan. My guess is that his army experience was such a different reality from his normal academic life that this dementia, caused by Alzheimer's disease reminds him of that other time of his life where he was able to make the best of a bad situation by getting promoted to company clerk and not having to spend time preparing for combat of any kind. Sadly, he is pretending he has those skills, that he is making those decisions, that he is living that life now. Good for him!!!