People interested in the discussion between Eliezer and Richard might find this Wikipedia article interesting: Depersonalization Disorder

Essentially, people behave as they otherwise would, except they don't have a sense of "self-awareness". That is, they did something, and they know they did something, but it doesn't feel as though it was them who did the thing. Often people feel as though they are automata, pre-programmed to respond to certain stimuli, but that there is no "self" driving them.

The disorder also tends to cause its inverse, which is derealization. That is, the individual perceives himself to be real, but nothing external is real.

This effect can be generated with drugs, and it can also be treated with drugs. This suggests to me that the entire "sense of self" is caused by a chemical interaction within the brain.