Of consciousness and death

(Originally posted by Jason in 8/2012)

At the end of last month, John Templeton Foundation generated some buzz by awarding $5 million to University of California Riverside philosophy professor John Martin Fischer to lead "Immortality Project" to investigate questions such as (quoted from the website)

• whether and in what form(s) persons survive or could survive bodily death
• whether and to what extent persons’ beliefs about immortality influence their behavior, attitudes, and character
• why and how persons are (at least pre-reflectively) disposed to believe in post-mortem survival
• whether it is in some sense irrational to desire immortality
• and more besides.

While these questions sound innocent, there is no shortage of causes of concern, some from the statements from the project lead himself (careful documentation as a valid approach to determine whether near-death experiences offer plausible glimpses of afterlife? theology as a way to bring reason to beliefs about religion?). Most importantly, if you don't have a clear idea about the conscious life of Homo sapiens, how can you meaningfully talk about afterlife? (this last sentence, of course, is paraphrasing Confucius' take on this topic.)
Unfortunately, understanding of consciousness requires progress in neuroscience, which doesn't generate news everyday (optogenetics -- Method of the Year in 2010 -- deserves some attention). We can, however, anticipate what we expect to find. For some of us, that may in fact suffice.
What do we expect to find? We expect human consciousness to be an emergent phenomenon, fully described by the underlying physical system. This position is variously referred to as "scientific materialism", "physicalism", or "mechanism", but it really shouldn't be considered merely a "position" or "school". People have been looking very hard for things they don't fundamentally understand, went so far as to build a machine kilometers in diameter in order to find phenomena they can't describe, and ended up only validating what they hypothesized so far. While there is still hope that something new will be discovered at LHC and what we know so far shouldn't be considered perfect knowledge, it's no longer rational to place your bet on something mysterious at play for our consciousness. We expect consciousness to be fully explained by the function of your brain and (to a less degree) entire body as much as we expect the sun to rise tomorrow morning, as long as you live far away from polar regions (In case you are wondering, this is not induction as much as Bayesian inference. We are estimating probability given imperfect knowledge).
A few conclusions immediately follow. Since human body occupies finite volume and contains finite amount of energy (there are some unfortunate outliers of the distribution, but they can only get so large and still be alive for long...), the set of possible "human states" is not only countable, but finite in the most precise sense of the word, due to quantum mechanics. As you may have guessed, this set of possible human states is unimaginably large: we are trying to describe a system which typically reaches 60~80 kg by quantum mechanics, which describes individual electrons and photons. However, this set of possible human states is further constrained by our knowledge in biology, and many human states are identical for practical purposes, even though they are, strictly speaking, physically distinguishable. For example, human genome is already sequenced, and it turned out one's genome can be compressed and sent as old-fashioned e-mail attachment (~4mb): your genome can only differ so much from the reference and still qualify as homo sapiens. The molecules in your body that do not participate in the flow of matter and energy are in thermodynamic equilibrium with its environment, at around body temperature. For the ones that do, the bulk of free energy used comes from glycolysis and citric acid cycle. Since no biochemical reaction reaches the energy scale of gamma ray, its occasional presence due to radioactive isotope or cosmic/solar radiation is of no relevance except the possibility of cellular damage, and so on so forth.
What do all these mean?

1. While the number of possible human states is without doubt still vast, each individual is no longer unqualifiedly unique. We can consider each one of us at a given instant occupying a specific human state, within a intrinsically shaped "human phase space" constituted by all of the possible human states. Our lives can be considered trajectories through the human phase space: by most measures of distance, we start very close to each other as fertilized eggs and then drift away from each other (continuing the theme of Confucius). We enter the subspace of self-aware humans around age 2, roughly follow the development program with environmental influences, and finally drift out of the human phase space, i.e. death.
2. Subjective experience is in fact replicable in principle, and such replication goes as follows: the initial preparation is the easiest, all you need is an sufficiently identical egg (effectively fertilized egg with the same genome, epigenetic markers, the same number of mitochondria with the same DNA content as the original, perhaps approximately the same number of glucose and ATP, and other relevant variables). Then you have to follow up with sufficiently identical environment: in utero, childhood environment and beyond. The resulted subjective experience of the replica would be the same except the inherent uncertainty of human state and variation in preparation. Some of the attempts may end up very different, but with sufficient number of attempts some are bound to end up eerily similar or for all practical purposes, identical. If we can run an ensemble of these replicas of the original as computer simulations, we may even be able to apply particle filter algorithm to localize the one closest to the original.(Disclaimer: above is intended as thought experiment. In reality such experiment could be cruel to the replica and prohibitively expensive, compared to whatever it may accomplish.)
3. In the real world, the closest example is "identical" twins. If you have a identical twin, your twin is not only similar to you. With soul or other mystical element out of the picture, you can consider your twin genuinely close to you in the human phase space, or even "almost you" if your upbringing is sufficiently similar.

Up till this point, these conclusions and implications should be at least technically true. It is, however, up to each one of us how we are going to take them. Personally, I actually feel somewhat relieved to realize that I am not responsible for something immaterial, intrinsically unique, and irreplaceable: there is no such thing as "soul". I will never be reincarnated into, say, an insect being eaten alive from the inside by parasitoid or some kind of gruesome being called Preta. Supposedly I may try to extend my life in the future if I feel like it, but honestly I don't really like everything about myself unconditionally (I doubt many do) and many aspects of the environment I experienced. I may try to "edit out" these aspects of myself and environmental influences in the future, but exactly how worthwhile is such self-preservation and self-improvement? After certain point, how much continuity is left between now and such future (interestingly, we apparently evolved a partial break in our stream of consciousness as we develop from an infant into an adult)? Might it not be more meaningful to make a clean break and start over, with (possibly genetically engineered) offspring and vastly superior upbringing?
I suspect each one of us would have a different take on this, so please leave yours as a comment (as long as you are a self-aware being, not a spambot!) If you run into my replica though, don't bother asking: he would say something almost the same :D
P.S. Oh, Pascal's Wager, you asked? That's really beyond moot. I suppose there is a vanishingly small chance that some kind of super-intelligent and technologically-advanced being is keeping track of us, scoring us along the way, and waiting to initiate two systems: one constantly inflicts excruciating pain upon the (unfortunately) chosen, replicated, and most likely modified human states, and the other constantly provides maximal bliss to the (fortunately) chosen, replicated, and modified human states. But why should I be personally concerned? I suspect if such dude shows up at this point though, most of us won't welcome Him, Her, It, or Whatever.