- what happens when a soul dies ? (aka Aizen's "murder" if it was real) would the entity just disappear forever then ? or reborn in the real world ?
- do people age ? it looks like souls age and die, except people with strong reiatsu seem to live a lot longer. case in point, renji and rukia were still in their teens when their friends died.
- why do people with reiatsu need food ? in order to fuel their power ? =P
a little sidenote: bleach's theory of afterlife and reincarnation can't apply to real life. they say that souls form a cycle going from soul society and real world, birth and rebirth. however, if that's so, how come the world's population is increasing exponentially?