OH, but we do know. Consciousness and personality has been directly linked to the brain. That's why various levels of brain damage can significantly affect memory and personality. At times people develop entirely different personalities. If consciousness was separate and survived death, this would not be the case. I get that it's hard to accept for some.
Nope.
We don't know what consciousness really is.
Neuroscience has only really just got started as a discipline and doesn't even know how to ask the right questions about consciousness.
The hard problem of consciousness is no nearer to being solved than 20 years ago. There are many philosophical theories like epiphenomenalism, functionalism, neutral monism, reductive materialism (identity theory), property dualism, some philosophers are even still substance dualists.
There is also the philosophical position known as
new mysterianism (colin mcginn, thomas nagel, roger penrose, noam chomsky), which in its most extreme form states that the true nature of consciousness can never be understood because of the paradoxical nature of the task-- the object of inquiry is the same as that which is inquiring into it, making it inherently unsolvable, .
Of course the brain plays some role in conscious experience, but the question is does it function more as a reducing valve or filter to a pre-existing (quantum?) consciousness, or is it more like a combustion engine which generates consciousness as a naturally emergent property?
Even matter, when you go deep enough, isn't really physical. It's about mathematics and forms and information and ideas.
And some physicists think that consciousness has a fundamental role to play at the quantum level in determining the properties of systems (e.g. copenhagen and von neumann-wigner ('consciousness causes collapse') interpretations of quantum mechanics). It's all still a mystery. No one really knows.
I get that it's hard to accept for some because people like to think that they know things which they don't or possibly can't know.
Thanks very much.
May as well (unsuccessfully, obviously) try to be humorous before I leave this godforsaken planet.