I think you’re talking here about qualia (the raw, qualitative aspect of consciousness). I agree we shouldn’t dismiss qualia with cheap eliminative arguments or reductions. That’s why I’m a property dualist. But it makes more sense to speak of consciousness than of spirit, because of the different connotations. “Spirit” is an anachronism and it misleads us into ignoring the monumental successes of scientific explanation.

I also think you’re overstating matters in saying no one knows anything about mental experience. Cognitive scientists know quite a lot, actually.