If I have given you the impression that I believe in a soul then I must not have been clear, but I do suspect that conciousness is unique to an individaul and bound to a body because I have so far seen no evidence to the contrary. And the idea that conciousness can be transferred is riddled with philosophical problems, the most basic of which are embodied in the questions I wrote in my last post. If anyone could please answer those questions for me then I feel like I would have a better understanding of where the "eternal mind" people are coming from.
Honestly I have found your explanation even more confusing. You seem to have confirmed some of my issues with the eternal mind, such as the fact that two copies of a mind would diverge into seperate people as soon as they started having different experiences. Well wouldn't they start having different experiences the second after they were created? So how is "making back-up copies" of your mind even possible? And while you say that there are "no dual-consciousnesses", dual-consciousnesses seem to be exactly what a lot of eternal mind people expect. In fact I think the existence of dual-conciousnesses is a critical element of the "eternal mind" theory. Without it how is the transfer made? And finally "two people with a lot of shared memories" doesn't mean they are the same person. My wife and I have a lot of shared memories but we each have our own distinct consciousness. If I die I will not perceive that I continue to live on because my wife is still alive. Neither would you perceive anything after death simply because there still existed a copy of you with "a lot of shared memories". That is not immortality.
Go to
http://en.wikipedia.org/wiki/RAID and specifically look at RAID 1. That is the simplest equivalent to what I'm talking about except imagine the mirrored drives are in two separate countries and are linked by a network.
Look its really not about having "your consciousness" continue to exist forever. At least not if we use your definition of a conscioussness which seems to be anything with a particular set of "memories, knowledge, and personality". Immortality is about maintaining an unbroken sense of continuity of existence. That may or may not be necessarily connected with what you are referring to as a "consciousness" but when I say "conscioussness" that's what I'm talking about. To me, that is "me". This feeling of self-awareness. There are plenty of simple thought experiments and even some real world examples that can confirm that two beings with the same "memories, knowledge, and personality" likely do not have the same sense of self. So when one dies they still go into oblivion while the other lives on.
I don't disagree with your points here but I have a few thoughts on how this can and must be done if the goals of those who gather here are to be met. Let's imagine the day has come when it is possible to run a high resolution MRI of a person's brain and upload their entire repertoire of memories, personality and individuality to a digital substrate (computer). You and I will agree that the digital copy might be neat but it's still not "them" in the continuity of consciousness definition. However let's imagine the technology advances a bit more and it becomes possible to hardwire a link via carbon nanotubes to each individual neuron of the human brain. At this point the computer would have instantaneous input that would let it keep the "copy" exactly up to date. If it allowed the copy to "run live" it might even have experiences and be able to update the wetware brain. However we're still not at the critical point. The critical point would come the day our wetware human decides his protein and myelin processor isn't going to cut it anymore. Perhaps he is diagnosed with early stage Alzheimer's. Alzheimers, in a guy who doesn't even like to sleep at night because of the loss of consciousness and control it entails. THIS is the critical point. The wetware brain was already effortlessly feeding information back and forth between itself and the digital side of things. The digital side is a complete copy and so "it" knows that it is conscious. The meatware knows that "it" is conscious. They both are fully synced. There is no differentiation of consciousness between the two. Both are taking in the same sensory input. The "consciousness" is fully merged. At that point a nanosurgical probe signals a region of the brain not involved in the sensation of "me-ness" to undergo apoptosis (controlled cell death). Let's choose the cerebellum which is involved in balance and coordination. This process is done for the benefit of the nervous presumptive uploadee. No sedation or anesthetic is involved as he is fiercely interested in making sure "he" does not disappear in the process. As the biological cerebellum atrophies away perhaps over the course of a couple hours the carbon nanotube connections take over signalling the body to maintain balance and sensory functions.
Our subject doesn't notice the difference so he gives the go-ahead for the next stage. The occipital lobe is next. It is largely concerned with processing sight and the digital processor is far advanced beyond it's abilities at this point of time so switching from biological control to the nanotubes only causes a slightly increase in visual processing ability. The process continues over the next several days. At each juncture the man digitizes a piece of his fading brain. However he ensures the process is ceased entirely while he sleeps at night. Finally all of the brain has been switched to digital control with the exception of the frontal lobe. The nanoelectrical apparatus is controlling the autonomic systems of the body, regulating heart rate and respiration. It is the sole repository of his memories. It is processing new sensory input and storing it to memory. The frontal lobe of the brain is the section that has been worried since the beginning about the risk of it's demise. However the parallel model of it in the computer is just as worried. After all, they are identical synapse for synapse, input for input, output for output.
Slowly, and with the knowledge that there is no other way to ensure his survival the man pushes the button causing the frontal lobe to undergo apoptosis.
Twenty minutes later it is done. The body has not moved. He lets out a deep breath. Alzheimer's cannot destroy him now. Indeed, if he keeps live synced copies of his consciousness in multiple locations on earth very little could. If he launches copies of his consciousness in various directions across the universe - all capable of reintegrating and joining into a single entity if they ever come into contact again - he will have achieved practical physical immortality. And, he'll never have to sleep again.
I really think this needs to be thought out in a little more philosophical detail here. Or at least I need someone to explain it to me in a little more detail. I need the nitty-gritty if I'm going to accept this possibility. Right now it just seems like a lot of vagaries and inflated hope in the powers of technology. Its almost a religious faith people seem to have that somehow its going to work out. Look "eternal mind" people. I want to believe. "Help thou mine unbelief"!
I hope this helped a bit.