Self awareness is a function of our evolved conscious brain. But why the sensation of an "I" or a "self." Why are we not just a robot without an inner voice? Why do we have the impression of having a little homunculus sitting behind our eyes, with whom we can engage and even talk with?
The supposedly immaterial soul, we now know, can be bisected with a knife, altered by chemicals, started or stopped by electricity, and extinguished by a sharp blow or by insufficient oxygen.