What do you think of the following opinion about people imagining things (like, in the case of an illness)?

I watched “Shutter Island”, who talks about precisely the thing I’m going to describe now, which upset me. The potential for this illness exists in all people and, under the right circumstances, any man or woman would be driven to the other side of madness. Perhaps, “the other side” may not be the best way to phrase it. After all, there is no wall between here and there. It lies on the borders where reality and UNreality intersect. It’s a place both close to him/her and distant to us. Sometimes, I have to ask myself this question. It’s true that to us his/her imaginings are nothing but the inventions of a busy mind. But to him/her, there simply is no other reality. Furthermore, (s)he’s happy there. So, if I were a doctor, why, I ask myself, why in the name of healing him/her must we drag him/her painfully into the world of our own reality?