I have heard of artificial hearts being implanted into people, but it doesn't make them any less human. At least it's better than having no heart at all. To begin with, I wasn't speaking of the heart in its physical form. More into the spiritual form.
If your brain get replaced, you are no longer yourself. The character, Data on Star Trek: The Next Generation may seem realistic, but he is not real. He is made to be like a human being. But he'll never be one because he doesn't have a soul. You have to remember that, we only allow ourselves to become emotionally attached to machines which already has happened to some.
Some people are emotionally attached to their stereoes, computers, DVD players, TV, etc. Don't ask me why, but some people are like that. Heck, I remember an article on a woman who was charged with manslaughter or murder because she tried to save her pet which was in the form of a Giga Pet machine or something and she got a man killed because of it.
If you want to be human, you need a soul... and a brain too. But if they somehow manage to make a machine that functions exactly, or better than an organic brain. Then, that'll be a different story. A brain is like a hard drive, it stores your memories, emotions, opinions, thoughts, and more. A soul has to be in control of it, your soul drives your body. Just like you drive a car.
But a soul is capable of making both good and bad choices. A soul can become tainted, most souls are tainted in a way or more to begin with.
Heck, when you die and leave your body. Only a portion of your brain are taken with you into a new life which is why some people are able to remember some details from their past lives, just like you are able to recover some data from an erased hard drive.
Yeah, that's a lot to discuss on.
