I disagree with your conclusion re that my explanation is a metaphor for thinking.
You wrote that's what it was. I quote: Therefore our human spirit in all its guises is a combination of the brains formulation of our desires and goals for whatever purpose and the way we bring that to fruition.
Now you are saying it's oxgygen? That is not at all what you said in the quote abov.
The first definition of the word spirit according to my dictionary is ; spirit noun, force giving life to a body.
No one has yet explained what that is yet. Simply saying it's oxygen doesn't cut it. There are things alive that don't breath oxygen. What if a life form breathed flourine or lithium?
Force in terms of physics is seen as an influence which can produce a change or reaction to a physical system.
Back up there. You just tried to take a definition that has nothing to do with physical things and turn it into one. You haven't connected the dots. And if you DO want to say life force = oxygen = force, then a bullet to the head can extinguish force, it clearly therefore must be a greater force. In fact, since oxygen is produced in the hearts of stars and only given to us via exploding stars which only happens via the coalescence of hydrogen which only happens because of gravity, you could easily make an argument that gravity is really spirit. Without it we wouldn't be here. Or the strong nuclear force. Or the weak. Or iron. Or the speed of light. Or neutrons.
At this point you are just picking of one the many things necessary for human life and going "that's it". It's random and arbitrary at best.
So far, we are no closer to an answer.