So does this mean that if one could emulated the function of the brain on a massive supercomputer, my mind would be running on this machine? Could science one day transfer all one's memories and neural pathways to a computer and thus we would continue to live on without the mind? Does science have any clue as to why I am me and not someone else(and you are you and not someone else)?

I completely agree with you, but couldn't theists just point to some sort of "soul" argument and just go from there? 

The fact is that the brain itself isn't going to die all at once.  Certain neurons will outlive others, regardless of if it is one second or two minutes.  Based on your argument, each "mind" will become progressively more aphasic as brain cells die until every neuron dies and there is nothing left.  There is no finite line between life and death, as you said it is a continuum.  When people are announced dead by a coroner, a large portion of them is still biologically alive.  These pieces of viable tissue, whether neuronal, muscular, or bone can still function with appropriate electrical stimulation.  So when does "death" happen?  Someone is deemed dead in various different states of decomposition.  In the case of an acute trauma, I would venture to guess that at least 10% of your brain cells could die due to lack of blood flow before you would actually pass out from hypotension. 

The examples go on and on.  I just realized your argument is hilarious, as if an afterlife existed everyone would enter it with severe cognitive deficits.

I am regularly consulted to see patients who suffered massive hypoxic brain injury (eg. secondary to cardiac arrest) and the issue of NDE is never raised in Neurology. NDE is heavily tainted with pseudoscience and thus there is no well designed objective study on this matter. If say a thousand atheists (and I mean hardcore like Dawkins, Hitchens or Harris) and a thousand theists were successfully resuscitated and asked about any recalled visual phenomenon, then this would be a well designed scientific study. And what about folks who are blind since birth? If they are brought back from the brink, what sort of NDE do they experience? I suspect that the majority of those who study NDE "scientifically" are supernaturally biased to begin with and are not truly objective.

Why unbreakable? That sounds like the old argument that the heart or liver or whatever is so interconnected with the body that attempting a transplant would be impossible. And yet, we have transplants.

There are two main boundaries between brain and body. One is, appropriately enough, called the blood-brain barrier, which prevents blood and other fluids from mingling with the cerebro-spinal fluid.

The second is less obvious, but no less real. It is the information barrier which can be represented by the synapses which separate the sensory and motor nerves from the central nervous system, especially the brain itself. What passes between two neurons is more or less simply a *signal*. The neurotransmitters are, appropriately enough, merely the transmitters of that signal. The signal itself is then filtered, amplified, and propagated by the neuron's internal machinery, resulting in what can only be called a *digital* nerve impulse. That means that the ultimate cause of the impulse is irrelevant to the effect of the impulse.

If surgeons cut out my eye and replaced it with a sophisticated camera, and an electronic-nerve interface which simulated the same nerve impulses my original retina would have produced, I would literally be able to *see* out of the camera. The camera may have to simulate various biological quirks like eye saccades and iris control, but these are quite doable.

This basic principle, if we imagined to connect every incoming and outgoing nerve from the brain to some appropriate piece of mechanical technology, is how you can imagine the information barrier between the mind and the outside world. This is the basis of the (in)famous brain-in-a-vat thought experiment. How do we know that we aren't simply brains in vats in some mad scientist's laboratory? Or, the Matrix? Or, my favourite version: How do we know we haven't voluntarily entered a game of world simulation, where we're on a kind of 'mind vacation' from the *real* reality which is very much unlike the one we experience here? Perhaps our human brains are simply simulated visualizations of the underlying computer technology which allows playback of the simulated reality to our *real* 'brains' in the *real* world.

Aside from that bit of fantasy, the principle that the information coming into our minds is independent of its specific source is quite solid. We already have several technologies which rely on this principle, though few that are commercially available.

So, what about the blood-brain barrier? The things that cross it are fairly simple: water, nutrients such as glucose, hormones, some drugs, etc. There is nothing here which is so crucial and so complex that it makes sense to say that the codependence of brain and body is unbreakable. Most of these things have nothing to do with the mind, and are simply life-support for the brain's biology. Even drugs and hormones only affect the brain as overall 'levels' which affect all the cells of the brain globally.

The real complex stuff happens across the information barrier, and this is finite and computable. Let's look at some specifics:

There are not 'infinite' neural pathways. The brain is decidedly finite. Each neuron has on the order of thousands of connections (synapses) with other neurons. This puts the brain somewhere in the neighbourhood (ballpark, you can google more accurate numbers) of trillions to quadrillions of connections. Yes, it is very big. No, it is not outside the realm of possibility for simulation with technology. We already have fairly sophisticated simulations of single neurons, and even some sophisticated simulations of large clusters of neurons. Again, the important thing is the information signal, not the particular medium (neurotransmitters) nor the life-support (water, nutrients, etc.). A neuron, from the point of view of the mind that it gives rise to, is basically a complex electrical switch. Quite complex, but not outside the plausibility of extremely accurate simulation.

A brain in a computer would not have any need of heart, lungs, kidneys, liver, or any other merely biological life-support. All it needs is a plug, a transformer, and an A/C outlet. Really, all it needs is a power source. There is nothing crucial to 'mind' that comes from the maintenance of this basic life-support. Some things, such as the feelings you get from various activities, for example the endorphins released from exercise, could be easily simulated as global 'levels' in the simulation software.

We may need to provide some form of motor control for the person to remain sane, but such control could easily be supplied by technology. Even a video-game interface into a virtual world would be a good start. Allowing the person to control a robotic body would be a step up from that.

How much time do you spend sitting in front of your computer anyway, with almost all movement reduced to holding an erect sitting posture and moving hands and fingers on mouse and keyboard? You're not telling me this is so stupendously complex such that we'll never be able to simulate it, are you?

We've learned recently that the brain is incredibly plastic. Whatever parts of the brain find themselves without use will quickly learn how to take on different roles to enhance the ability of whatever job neighbouring neurons are currently occupied with. 

Also, the 'body' we can provide a simulated brain could potentially be anything we could construct, real or simulated. Want to be a dragon flying around in a virtual world? We can do that. Certainly, if we can simulate a brain, we'll have the technology to make today's 3D games look like finger painting.

Sounds like a non-sequitur to me. We already have artificial hearts, iron lungs, dialysis machines, etc. The brain does not suddenly begin to fail when we replace its life-support with mechanical assistance. Helen Keller was blind and deaf, and yet she learned how to cope in the limited world available to her.

A simulated brain would not be cut off from the world, it would just have a different interface to the world. Not biological, but mechanical. Give it an internet connection, and its 'world' would expand probably bigger than even ours is.

The interesting thing about neurons is that they don't really have 'specific functions'. The adapt and learn whatever function is needed of them. They are like inter-changeable CPUs which are able to discover whatever information processing is necessary for them to perform. If they are connected to an eye, they will learn to 'see'. If they are connected to an ear, they will learn to 'hear'. There is a good deal of brain architecture which ensures that some neurons will be connected to eyes and some to ears, but the cerebral cortex is largely a blank slate. The lower parts of the brain are more hard-wired, but they do not account for the majority of the complexity of the human brain.

Most of that you wouldn't even need to simulate. And the parts that you would, you wouldn't have to simulate to any great detail. For example, you wouldn't need to simulated the chemical structure of a neurotransmitter, you'd only have to simulate how much of it is present in the synapse. And even then, you wouldn't have to be precise in the simulation; as long as the simulated neuron behaves digitally the same as a biological neuron, you've functionally simulated the neuron.

You can't perform math without stimulus from your digestive tract? What?

Say I was unlucky enough to lose all four of my limbs. Would I still be able to do math? How about if my liver and kidneys failed, but the hospital had technological replacements. Would I suddenly be unable to do math? How about if I lost my heart, lungs, stomach, intestines, spine, torso, and basically was just a head attached to a bunch of tubes and a supply of blood. Would I be unable to do math? What if, like Helen Keller, I was also blind and deaf. Would I lose the ability to add 2+2?

Say my only ability to see was to be able to see an 80 character wide by 50 character wide screen which was flashed symbols to my optic nerve, allowing me to read a simple unix/dos-like computer interface. And the only ability I had to 'move' was to move a simple flashing cursor around the screen, and to 'type' one of 256 possible characters at a time. And the only ability to 'hear' was to hear a simple 8 bit tone. No signals came from anywhere else. Would I be unable to do math? To read an email? To write a reply? To read an ebook? To write a book of my own? To explain why I don't believe in gods?

No. My world would at first seem quite tiny, but I wouldn't suddenly lose the ability to think. Any feedback I got from the outside world would be just as meaningful to me as we get from our relatively vast senses. I might even get quite adept at manipulating my little world. I might request that someone hook up my cursor movement to a control which moves a little robot around, and my 80 by 50 screen to a digital camera which converts images into ASCII art which vaguely represents what the robot sees, and my 8-bit sound-card to a little microphone, allowing me to hear vaguely what's going on wherever the little robot is. It would be a relatively impoverished experience, but the point is simply that I don't need a biological body to have a 'body'.

For the case of consciousness, it's even easier than that.

Where 'you' are, there is a brain hooked up to senses, and that brain experiences the world from where it is, and has memories from where it has been. That experience, and those memories, *are* you. Likewise, where 'I' am, there's a different brain with a different perspective and different memories, and those experiences and memories are me.

If my mind were duplicated and simulated on a computer, then I, here, would remain me. And the new mind where the computer is, and which experiences whatever it experiences based on whatever 'senses' it's hooked up to, would inherit my memories, but would begin experiencing the world from a different perspective and with different memories, and would no longer be identical to me, here. It would be me, there. And soon it would become not-quite-me, there.

Just like identical twins, sharing identical DNA, are not the same person, because they inhabit different bodies.

You are you because there you are. I am me because here I am. I'm not there, and you're not here. Easy.

I very much disagree.  The body is not exact.  A large chunk of personality and other psychological disorders stem from imbalance in NTs.  Also, the telephone analogy kind of oversimplifies the situation.  A mech-brain would be extremely complicated, and one reason is because of the algorithms developed to counteract nonsensical transmissions, like the one you provide.  I guess it could help cure psychological disorders if you think about it.  But yeah, the body and the brain are not perfect.  Basically all psychological disorders would disagree with you on signal perfection in the brain.  Ever have a headache? 

My point was that, if sophisticated enough (and providing science can fully explain the mind), it could.  That is why it would be hella-complex.  It would know how to factor in those nuances, by sheer nature of the fact (in our hypothetical future here) that we could explain all of the brain's activity.  If we know everything about the brain, what would stop us from incorporating that into the program?  Every example you give could, feasibly, be created as a program, if those functions aren't truly random.  I think our distinction would be here:  If there is a truly random component, then a predictive system built into robo-brain wouldn't be capable of mimicking bio-brain's outputs exactly.  It would, however, still be mimicking a human brain, and would consequently be a new brain, with just the slightest differences building up through time.  It would be a new you to experience the world differently from that point on.  The implications are freaky.

This is assuming that it is possible to learn absolutely everything about the brain.  Learning everything about a dynamic, changing, never before studied object is not possible.  Each individual brain follows a broad set of guidelines- not rules of practice that must be followed.  Three different workers at 3 different McDonalds will make the same tasting burger for you, but they aren't going to do it in the same time, with the same placement of the pickle and the exact same amount of ketchup.  Same with 3 different human brains: Same ingredients, different ways of getting to an end product.  It's not a case of "I've seen one, I've seen them all".

Just as much, the individual brain itself is always changing. Unless you could map every single neuron instantaneously cloning is impossible to do.  Think about it.  Say it took the brain-engineer a mere day to view every single neuron in the brain and determine its function (that's assuming there is some futuristic machine that could analyze billions of neurons in a day.  In order to do this, you would have to run the gamut of functions:  figure out which neuronal groups do large scale things like flex the shoulder, which ones help you remember where you live, and the tiny group that controls the ability to flex to distal interphalengeal joint of your pointer finger.  You would have to see which neurons fired during which movements (yes there is a general area of the brain where these neurons can be found in most people, but you need to find every individual one).  Even during this time it took to collect data, the brain is making new synapses, logging new information (This seat is cold, etc).  Neurons are making new connections with other neurons to store information, interpret input, and send responses.  Simultaneously, others are disconnecting (trivial information not needed, forgetting whether the building he just walked into was white or red, basically anything).  For sake of argument, lets say the scientist started anteriorly and worked posteriorly.  By the time he was done, the prefrontal cortex map might have radically different synapses from that of the occipital lobe.  If you want to put it in terms of technology, it would be like this forum filled with a whole mess of broken hyperlinks. 

Broken hyperlinks cannot get you from point A to point B, you only end up stuck with a white screen.  I just don't see it, but it's a fun hypothetical idea.

 Do androids dream of electric sheep?