So I'm not one of those atheists whose writings I've read who want to purge the word spirit from rational discourse because it's supernatural. It certainly is NOT supernatural as far as I'm concerned. But, as far as I'm concerned, it is only a phenomenon of human perception. There are no spirits absent a human to perceive them, just as there are no colors absent a human to perceive them. Colors and spirits both, and many other such things, are the functioning of the human nervous system in response to physical stimuli. Colors are not visible electromagnetic radiation, colors are the visual system's response to visible electromagnetic radiation. (I think this example is very useful because there is not a one-to-one correspondence between electromagnetic frequencies and perceived colors, i.e. one color can be various combinations of frequencies.) Spirits are not complex systems with certain attributes that are very interesting to many humans, they are not even a part of those complex systems, they are those affected humans' responses to those systems. (And then there's God which seems to me to be the human mind's response to itself, not that I can make this observation from having had the experience of the response myself.)

How does my understanding of spirit support an idea of spiritual or spirituality? It once occurred to me that spirituality can denote two closely related things: one's emotional relationship to the world, i.e. one's creation and appreciation of spirits, along with one's cultivation of that relationship; and one's cultivation of one's own spirit, that is, cultivating how one creates one's own spirit based on one's experience of oneself as well as attempting to cultivate or design the perception in others of one's spirit.

I maintain that many people attribute supernatural characteristics to spirits or spirituality because their awareness and understanding are limited, and they will readily believe ideas which are not included in their awareness and understanding, a tendency shared with the majority of humanity on this planet. Maybe I should add here that I don't think I am free of limitations on my awareness and understanding, but it does seem that I am not led to believe anything not supported by my awareness and understanding no matter what I imagine. This is not intentional, it just is so, and this leads me to suspect that the tendency to believe ideas not supported by awareness and understanding is an unalterable spiritual trait. (Should I have used the word "personality" instead of "spiritual"?)

Examples of use of the word spirit which don't imply (to me, anyway) anything supernatural:

An Axiom of Spiritual Calculus: the spirit of a relationship is not a combination of the spirits, it is the spirit of those combined.

He's the spirit and image of his father.

We're following the spirit if not the letter of the law.

Typical version of the last verse of "Streets of Laredo":

Go fetch me a cup, just a cup of cold water
To cool my parched lips, the cowboy then said
Before I returned, his brave spirit had left him
And gone to his maker the cowboy was dead

Won't someone please bring me a glass of cool water
To quench my parched lips this young cowboy said.
But when I'd returned with the glass of cold water
The spirit had left him, the cowboy was dead.

Analogously to the last line of that verse one could say "The colors had left it, the rainbow was gone", and the analogy holds when we don't know which of the constituents required for a rainbow to be perceived are no longer present. Are we to abandon the use of the word "color" just because there might be those who insist that the colors of the rainbow have gone somewhere to exist on their own independent of the requisite constituents including their perceptual system?