I had originally started my last post wanting to talk about what I think about the mind/body problem, but got derailed with what I (maybe narcissistically) thought was an interesting story about how I got where I am. With that out of the way, I'd like to discuss how I think the mind/body problem arises and what can be done about it. This is largely a rephrasing of what David Chalmers had to say about consciousness in The Conscious Mind (1998), but I hope it's helpful anyway.
Chalmers spends a long portion in the beginning of his book discussing Philisophical Zombies (or p-zombies, see Wikipedia and the Stanford Encyclopedia). The idea behind a p-zombie is that unlike regular zombies it behaves externally just like a person: eats just like a person, laughs just like a person, etc. but internally it is devoid of consciousness. If you were to take this idea way too seriously, you might wonder whether other people in your life are actually conscious or just p-zombies, but please don't do that.
So if we don't think they really exist, why talk about p-zombies at all? The reason is that given the current scientific perspective, everyone looks more like a p-zombie than an actually conscious person. Science so far has done wonderfully with reductionist explanations of things we observe. Why is the sky blue? Because the air in the atmosphere diffracts light in a certain way. Why does it diffract light in that particular way? Because of the mixture and arrangement of its atoms. Why do atoms behave that way? Because they are made of electrons protons and neutrons that behave a certain way. I'm not sure I could keep going with this too much longer, but at some point you get to quantum physics, which is ludicrously accurate at predicting the behavior of very small objects, and we don't have anything at a smaller scale than that. So given that very low-level theory, we should be able to put together pieces and get a human. Start with quantum stuff, work your way up to atoms, build up atoms to proteins and other complex chemicals. Those chemicals sit an a lump called a cell. Some cells that we particularly care about (neurons) have excitable membranes that change voltage very suddenly. That voltage change gets transmitted along the neuron until it gets to another cell and either transmits current directly into that cell or releases neurotransmitters. Then the next cell gets excited and the process continues. Getting into the neuroscience side of things now, we know that the spiking of some neurons are modified by inputs to a human (sensory stuff like touch, taste, sight, hearing, etc.) and that other neurons spiking causes our muscles to undertake the actions we humans take as well as controlling a bunch of stuff in the rest of our body. Combine all that with the fact that we can prove that a large network of simplified neurons can compute anything (yes, anything, so long as the network is big enough) and that means that baring working out the (ludicrously complicated but not metaphysically mysterious) details we have a really good theory to explain human behavior entirely.
But hold on, we now have a model that is a bunch of entirely unthinking unconscious particles following basic laws in an certain way to produce actions that mimic thoughts and consciousness. That sounds like... a p-zombie! One solution that you might hear a lot is that mimicking consciousness IS consciousness. I think the phrases "We're just a bag of chemicals", or "love is just a hormone in your brain" are both sentiments that reflect this idea. Another solution is to say that your brain makes you believe you are conscious but you really aren't. This seems like a cop out, since it denies one of your most basic direct experiences. These explanations don't explain why it is different to actually be you instead of being an external observer.
The correct approach when you see this kind of a contradiction between your model of the physical world (which is essentially a p-zombie) and reality (the fact that you do in fact have conscious experiences that aren't just a behavioral or computational trick), is to first recognize that your model is incomplete and then look for ways to get data to guide you in improving your model. Chalmers suggests trying to correlate what people report themselves as being conscious of as a start for getting data, which I think is a good place to start. Then, after figuring out many of those ludicrously complicated but not metaphysically mysterious details I mentioned earlier, we might be able to see what physical reactions or computations correspond to conscious experience and go from there.
I love having this framework in my head to remind myself why all the intricate details of the physics of the brain are guiding the human race towards an understanding of something that has mystified us for so long. It's an awesome project to be part of.
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