The reality is likely to be that none of us knows either! But by knocking the subject about we may be able to creep up a little closer to an answer that looks a real possibility once all the least likely suggestions have been eliminated.

The other reality is that it doesn't much matter if we do know but extrapolating that argument it doesn't much matter if we know about many other spiritual aspects either. But humankind is an enquiring and curious beast and without that attribute it wouldn't be where it is right now, be that good, bad or indifferent! So we continue to try to fathom the many mysteries of life, of death and then what follows.