I don’t have to know everything that’s possible to know that some things are impossible and ghosts are impossible. Not only because they lack any medium which could generate consciousness but because they lack any matrial substance at all. If they are not matter and they are not energy then they don’t exist, by definition.
It’s not just consciousness which is a problem, by the way, it’s also sensory perception, memory and locomotion. Can a ghost see and hear? If so, how can something with no material substance interact with light and soundwaves? Can a ghost remember things? If so, what does it remember with and how does it store those memories?
Consciousness pretty much IS sensory perception + memory and a ghost is physically incapable of either of those things.
Incidentally, if a ghost can see and hear and remember, then why do people need brains and eyes and ears. Why the physical redundancy for stuff we can do with our “spirits?” Why can’t blind people just see with their ghosts?
Also, how does a ghost move around? Locomotion requires both energy and some kind of physical interaction with the environment. What does a ghost use for energy and how does it interact with the pysical universe in order to move around? If it can’t touch anything it can’t move, pure and simple.
The standard answer to these questions is the fatuous claim that we don’t know absolutely everything, therefore we can’t say anything is impossible. I call BS on that. If we can’t make any a priori assumptions at all about what is possible and what is not, then we can’t do science at all. There are literally an infinite number of prima facie impossible hypotheses – all with exactly the same amount of evidence as what exists for ghosts – for virtually any observed phenomenon, even the most mundane. Who left the toilet seat up? Was it a male living in the house or was it telepathically raised by a superintelligent rock on Mars? Can we rule out the latter possibility as patently absurd and nonsensical and dismiss it out of hand or do we have to seriously consider it because we don’t know everything there is to know about consciousness or whether rocks can be intelligent or whether telepathy can exist? Ghosts are actually LESS possible than intelligent rocks. At least rocks have material substance.
Imposing an irrationally absolutist standard upon what may reasonably be called “impossible” is specious and counterproductive and childish and scientifically impractical. Some things are so wildly, astronomically unlikely that it is perfectly reasonable and fair and indeed necessary to rukle them out a priori and give them no thought, especially since there are an infinite number of such hypotheses for virtually all of our life experiences.
I sometimes use the analogy of crime investigators. Should detectives puruing a serial killer entertain the idea that they may be chasing a werewolf or a reanimated mummy or a ghost, or is it safe for them to completely ignore any and all (of the infinite number of) hypothetical supernatural explanations and just pursue the natural?
What is it about the ghost hypothesis for spooky sounds or whatever that makes it a preferable explanation to the influence of telepathic Martian rocks? There is the same amount of evidence for both.