Here's a good point from David Morrell:
"We call a fully drawn character "lifelike" when in fact we can never know someone in life as well as we have known that character in fiction. To the degree that we are privy to a character's thoughts and emotions, the experience is totally unrealistic, however magical."
He's right on here. In the real world we never truly know what is inside of another person. We can't read their thoughts and can't even trust our reading of their emotions. How ironic that in "fiction" we can do both.