I just came across an ongoing debate between Bryan Caplan and Robin Hanson. The usually razor-sharp Caplan may be out of his element on this one, as he responds again to Hanson's response here. It will be fun to share some thoughts on this. First, here's a sliver of Caplan's position:
In any case, suppose we took neurology as seriously as Robin claims to. The right lesson to draw would be that thoughts and feelings require a biological brain. There's no way you can dissect a brain, then infer that a computer program that simulated that brain would really be conscious. That makes about as much sense as dissecting a human brain, then inferring that a computer program that simulated a brain could, like a real brain, be poured over a fire to extinguish it.
Philosophy is not for everyone. Nor is it, generally, for economists. But let me see if I can offer a few pointers to those, like Caplan, who would wade into these debates:
First, if you believe in disembodied souls, this is not the debate for you. Why? Because a commitment to the existence to non-physical substances is not something we can argue about unless we can agree on the meaning of terms like 'physical' and 'substance'--i.e. a basic agreement on what it means to be physical. A substance is a) something that exists, and b) something that is causally efficacious. Turns out both of these are necessary properties of physical things. The Cartesian would disagree with such tautologies for reasons of faith in souls. And faith is usually a philosophical conversation killer.
Now, let's see if I can dredge up basic criteria for physicalism (that way we don't have to trifle with lingering Cartesianism) and let the debate be about the relationship between mental and physical properties. I seem to remember some criteria, though admittedly it has been over a decade since I did any work on this:
I) That which exists, is physical, which is also to be causal. For something to be physical is to exert itself causally in the universe -- some how, some way. Descartes spoke of "substances" that were non-physical, causally interacting with the world through the "penial gland". But as we said above, this is absurd. That which exists is physical. Similarly, the universe is causally closed--that is, no physical event has a cause outside of the physical domain (e.g. what's wrong with Cartesianism). Ps can cause Ps and Ps can cause Ms. But no Ms can cause anything.
II) Supervenience.The mental supervenes on the physical. The relationship of supervenience is critical because it unpacks the tight ontological connection between some mental state M and the underlying physical state P (for, say, experience z). Any change in M will necessitate a change in underlying P, but not the reverse. The supervenience relationship is asymmetrical for the reasons Hanson suggests. (For example: silicon or other substances could instantiate certain causal-physical properties normally instantiated by biological gray matter. Bryan's software example is unideal because it intuitively distracts us from how M would be instantiated in the new P stuff (call it P'.) After all, lines of code are not instantiators, but information about what is to be instantiated in some physical stuff--like an android.
III) Dependency. The mental is dependent on the physical in the sense that no mental event can arise independently of some causal-physical substrate.
It may seem as if I'm being unfair with these criteria. But these seem to me to be basics of any respectable mind-body physicalism. So, Hanson may be correct that life extension is possible through replicating causal-physical processes a la functionalism. In fact, the real arguments lie in questions of whether mental properties are identical with causal-physical properties of the brain (rather than m/p identity of early physicalism). Hanson's life extension is basically a functionalist view, where the causal-physical properties of, say, "Bryan Caplan" are preserved (where "Bryan Caplan" is the sum of all the M(s)).
Now, there are associated problems of identity -- such as the persistence problem Hanson highlights in this video. But these are mostly separate problems. We may have to live with the fact that the referent "Bryan Caplan" is a collection of mental properties that are identical with certain causal-physical processes--all of which can be duplicated (even replicated time and again) in other forms of matter. (Imagine a bifurcating tree of Bryan Caplans, each of which will have their own superscripts (prime, double-prime, etc.) after replication.) In any case, I think all this boils down to the fact that Robin Hanson is a functionalist and Bryan Caplan is a dualist, who, unless he espouses some slippery (and obscure) form of dualism (like Chalmers's) believes in, well, spirits in the material world.