Hm, you bring up an interesting point. I think a brain has an essence and having a defunct concept of self would hinder that essence of functioning properly. There is a physical aspect here in which you could measure mental instability through neural pathways, etc… I agree with what you are saying though; is mental stability simply conforming to reality/society or is there more to it? I’ve personally though as mental instability as anything that hinders you from fulfilling biological needs.

I feel this article is neglecting a lot of psychology. Sense of self is very important to maintain mental stability. The brains thoughts and pathways are largely connected to the concept of the self.