The Observer, aka The Knower

I've been reading a (simplified) English translation of The Bhagavad  Gita   Today, in the 13th chapter, I came across the concept of the self as knower, which is similar to the psychological construct of the Observer.  Here are some quotes from the Gita:

"Think of the body of creation as a field, think of the part of you that is aware as the knower."

Then, after reviewing the senses:

"It is in this field...that desires, aversions, pleasure and pain arise.  The body, the intellect and the will rise also from this field.  Those who know this are unmoved by pride or deceit.  They are gentle, forgiving and filled with inner strength.  Those who know they are knowers are free from selfish entanglement. ... They enjoy solitude.  They do not run with the crowd.

Then this:

"Both the field and the knower are endless.  The knower is the source of every action, but the field is where sensations exist.  The knower witnesses it all. ...  The knower, [the] true self, ... neither acts nor is touched by action,remaining untroubled even though it is in all of life.  Those who see this find peace."

This concept of the dispassionate, immutable knower/witness/observer jumped out at me not because it was a profound new concept, but because it expresses something I have experienced.  Long before I read any psychological or spiritual exposition of an observer phenomenon,  I became aware of my self as that which knows/observes all that I do and feel but is itself non action and non emotion and without judgment.  I have always felt this "observer" to be my true,eternal self, and when I am able to transcend my affect and exist as observer, then I can know peace.