Most philosophical materialists who investigate the hard problem of consciousness accept that consciousness is associated with matter being arranged within certain bounds: a central nervous system with inputs. Change that arrangement, and you will change or destroy consciousness.
This leads to thought experiments like the transporter problem. If a device exists which can break down the atoms that compose your body and send them somewhere else and recompose them in the same form, many (most?) thought experimenters would argue that the person produced at the other end is not you. This is my position; you're dead the moment that you get broken down. Certainly the person at the other end will step out with all your memories right up until the moment of breakdown and say "Was I ever silly to have doubted that!" - but you are dead. If this seems unclear, imagine several possibilities.
First is that the transporter malfunctions and sends a copy of you (same atoms or not) to the other destination, without breaking you down in the first place. Are you suddenly seeing out of four pairs of eyes simultaneously from both destinations? Another way to imagine it is if it were very low-tech: you're broken down into atoms, and someone records all the information about the arrangement of the atoms in your body with paper and pencil. This record is then sent by Pony Express from St. Louis to San Francisco, in which city chemists laboriously reconstruct "you" from the formula. Again, assuming the technology to perform such a feat chemically ever exists, certainly the person who wakes could honestly say "Wow, the last thing I remember was being broken down in St. Louis, and here I am in San Francisco two years later!" First, the (real in this case) continuity of memory cannot itself be an argument for the continuance of subjective experience - if we load up someone else with your memories, does that make them you? If we load up someone with false memories, does that mean the false life thereby represented actually happened, and the person in those memories is now reified? Certainly in the Pony Express transporter, a person will wake up in San Francisco with your memory, who thinks s/he is you, and is physically identical - but you won't ever wake up again once they take you apart in St. Louis.
Would it make a difference if the chemists in St. Louis send not just the instructions, but vials of the actual atoms of carbon and nitrogen and oxygen they got from your tissues? Self-evidently not, and atoms are equivalent anyway (unless we're going to suppose some elan vital or special consciousness juice for them. Which we're not.)
It's also worth comparing your post-disassembly fate, as a conscious human, to that of Hernan Cortez's ship. He had his men disassemble the ship at the shore of the Gulf of Mexico and carry it inland and uphill hundreds of miles, to be reassembled it in Lake Texcoco to attack the then-island capital of Mexico (yes, this is really what they did!) There was a ship in the Gulf; then a bunch of wood and nails and rope, but no ship getting carried up from the lowlands and back down to Tenochtitlan; and then again a ship in the lake. Where was the ship during the trip? A ship is just a certain arrangement of elements - so it was nowhere. The crucial difference is that a ship has no experience; there is nothing it is like to be a ship, so there is no property to be lost in the transport, regardless of whether they send the original wood and rope or just a set of instructions so the conquistadors can build another ship when they get to the lake.
The problem with the transporter thought experiment is this. If our continued experience is a product of the continued functioning of a specific material arrangement, how can any of us exist for more than a split second? Every second of every day some of your brain cells are dying, some of them are building new connections, molecules are being delivered or carried away by the cerebral vasculature - that arrangement is constantly changing. And yet, of course, despite each specific material arrangement of the brain being constantly destroyed moment-to-moment, we seem to be continuously conscious.
There are several possible ways out of this conundrum.
- The transporter-kills-the-old-you position is incorrect.
- Our seeming to be continuously conscious is an illusion. Each of "us" exists as a conscious entity only for mere fractions of a second, but we cannot tell, because we still have the entire memory of the last incarnation, and of course we're not conscious of our own immediate extinction.
- There's a limit on how much rearrangement can occur to your brain and allow continuity of experience. On one hand, these sorts of absolute differences in kind (rather than spectra of degree) are usually suspect. On the other hand there clearly are limits to the changes that can occur to tissue and allow persistence of the self.
The last option is the most attractive but it suffers from some of the same problems as does property dualism (a more respectable name for panpsychism). For example, if your brain as it is in this nanosecond is conscious, presumably that doesn't preclude your brain as it is in this nanosecond minus exactly one neuron in the dorsolateral prefrontal cortex from simultaneously being conscious (and so on in some enormous factorial function that gives all the possible combinations therein). If this is true and each arrangement is conscious discretely, either a huge number of conscious entities exists co-dominantly within any one brain, or the vast number of human consciousnesses are locked away, looking on from inside as one lucky combination of cells interacts with the outside world.
Asking these kinds of questions allows the problem of philosophical zombies to invade one's own skull. There is no way for any of us to determine that any other living thing has subjective experience of the world. As a thought experiment, imagine wiring your own brain up to a friend's, from whom you would receive all of their impressions of the world (a la Being John Malkovich). You would find that you were certainly having an experience not only of your friend's senses but of thoughts, memories, reactions to those subjective experiences, and so on - but the issue is that again, you have no way of knowing if you're "contaminating" your possibly-zombie friend's brain with your subjective awareness, if anybody was home in the first place or if you're just experiencing dead inputs and your own consciousness is imbuing those inputs with subjective experience. You could ask the same question of an inert, 100% certainly-unconscious piece of matter like an eyeball. On its own, and eyeball is not conscious. Wired into your brain, it is providing the raw stimulus for a subjective experience of vision, but only that - the eye itself cannot be the source of experience, only a source of information, if the two have no overlap. Given that on its own the eye is just a photochemical transducer, we might even reasonably ask why we would consider the eye to be the generator of experience, and not the flowers the light is reflecting off of, or the sun that's producing the light in the first place.
We can ask the same question about wiring up to your friend's brain or a new eyeball as we can with new neurons. Imagine the frightening event that you have a severe stroke, and lose large portions of your frontal lobes. Now also imagine that after an intensive surgery, your brain is repaired with frontal lobe sections from an organ donor. The same argument applies; is the new lobe capable of experience on its own, or did your remaining brain "contaminate" what was previously a zombie lobe? (And does consciousness always win, or might a zombie lobe overpower the conscious lobe into zombiedom? If a question seems silly, it probably is; such is usually the case when we dig deeply into the assumptions that make us accept differences of kind in nature.) More realistically - you're conscious now, yet your consciousness is built out of parts that are certainly not conscious (or at the very least much less conscious) than you are. And that's not all - "you" were not always capable of consciousness and in fact, the arrangement that is you was not even always capable of consciousness. There was a time when you were an embryo and did not even have neurons, much less a brain.
This has become a reductio ad absurdum. The question of philosophical zombies is meant to question to basic assumption of materialist accounts of consciousness, that a certain kind of arrangement of matter is what creates (or enhances) consciousness, and if two identical constructed identities differed in their degree of consciousness, the materialist account would fall apart. But once we assume that there is even one consciousness entity, then to assume that there could be zombies, or even that a part of the world is unable to provide subjective experience, we must make arbitrary distinctions outside world and central nervous system - while forgetting that the CNS is made up of discrete combinations of elements which in isolation are certainly not conscious, and which themselves originated from an experienceless state. Why assume another human brain that you're wired to, and which is now a causal factor in your experience, is a unique topic for the question of zombiehood, and your contamination of it with your "core" of consciousness? By having an experience of a flower, are you not contaminating the flower with your consciousness in exactly the same way? If it was not capable of interacting with you in an experiential way to begin with, even if it's depending on your eyes and brain to complete the experiential equation, you would not be able to have a conscious experience of it. Extended most generally, all information must be able to provide experience.
This is one approach to solve the problem of second-to-second changes or 1-cell different combination differences causing discrete consciousnesses. Any combination or arrangement whose elements have the basic requirements for consciousness is conscious (there can be no zombies then). Although consciousness can be profoundly reduced as with transporter decompiling, as long as the core basic requirements of the arrangement of entities is met, there will be continuous unified experience. This is also consistent with the panpsychist or property-dualist position advocated by Chalmers, that experience is a basic property of reality, and like gravity, consciousness changes its quality in response to aspects of matter around it.
Consciousness and how it got to be that way