How are Dark Mtter and Consciousness different from Spirit?

[Angrboda]

Dark matter, spirit and consciousness are all hypothetical existences that cannot be directly observed, but only inferred as explanations for that which can be observed.

Right off the bat, there is an implied parity of observational weight or volume (and nature) between the three that isn't representative of the actual situation.  

Consciousness is not hypothetical, and is directly -and- indirectly observed to such an extent that it's inclusion in this list of three seems absurd.

Dark matter is an open hypothetical, and is indirectly observed.

Spirit is a thoroughly discredited hypothetical, that has never been directly or indirectly observed - and worse, a hypothetical whose purpose for existence has long since yielded to more accurate and factual explanations.

Yes, but why is it discredited? Saying that it is discredited without giving a reason why is just an argument from consensus. And I would have to disagree with your assertion about consciousness. If by observed we mean witnessed by our perceptual systems, consciousness as a brain process has never been observed directly. That places the hypothesis that consciousness is a brain process in the same category as the explanations that involve dark matter. There is indirect evidence, but no direct observation. Which is the same situation in which the hypothesis about spirits and souls is in — there is indirect evidence but no direct observation. So your tripartite scheme collapses into itself.