Consciousness. No-one has a handle on this -- at least not in the scientific world. What "space" does it inhabit? Does it extend past my corpareal body? Can it overlap with another's?
Sam Harris has discussed how our consciousness can be effected by trauma. Is that the consciousness, or is that the medium -- the brain?
I know my dog has consciousness; so how common is it? does it extend down to all living things? The Gaia consciousness? The hippy consciousness?
Stars and fundamental particles I accept (I don't understand, but I'm willing to go along). But "consciousness"? What is that?