Just as people who experience brain damage end up changing to some extent, depending on the extent of the damage, so do people change when their bodies change. A complete replacement of the body-below-the-neck (as in e.g. brain-only cryopreservation) would probably change a lot as well.
This seems like evidence against embodiment mattering that much if anything. If you lost both of your arms and legs, had your heart and lung transplanted and your spleen removed, you would be... likely significantly more depressed due to the whole "bedridden and permanently on immunosuppressants" thing, but still you, even with something like 30-40% of your original body mass removed or replaced. But if you had a comparable chunk of your brain damaged or removed, odds are you might experience significant personality or cognitive changes, or downright become a vegetable. That says a lot on what matters most.
If you lost both of your arms and legs, had your heart and lung transplanted and your spleen removed, you would be[. . .]still you
This sounds like assuming the conclusion, though the heart, lungs, and spleen aren't the examples I'd go with. The original claim was about "a complete replacement of the body-below-the-neck", and the first two places I think of when considering that are the spine and the gut. Even if neither of those places store intellectual cognition, they seem to hold lots of learned information in a way that would be difficult to replace. So, it seems reasonable to say there is some sort of identity, some 'me', in there, even if it's not the kind people usually mean.
Plus, what matters most for identity is pretty subjective. If you spend a lot of time training your arms and legs, having them taken away would seem more of an identity crisis, more like taking away a you-ness. Certainly the Two Arms and a Head guy thought so.
The original claim was about "a complete replacement of the body-below-the-neck"
Well, that's beyond current technology, so I compared with the best thing that we can think of - a partial removal/replacement of the body compared to a partial removal of a similar fraction of brain mass. Though I would also say that the fact that we talk about replacement of the body below the neck and not above the neck, despite the disparity in mass, already pretty much settles the question, because we all actually know full well which part has the lion's share in being "you".
If you spend a lot of time training your arms and legs, having them taken away would seem more of an identity crisis, more like taking away a you-ness.
For that matter, if I preserved my bodily integrity but suddenly was divorced by my wife, lost my job, was deprived of all my financial assets and was shipped to a foreign country where I don't speak the language, I'd probably have an identity crisis too. Does this suggest an even broader theory of embodiment in which my wife, my workplace, my bank account and my country are all parts of my body?
The weak form of the embodiment claim is "the brain/mind is affected by its surrounding contour conditions, first among them the chemical environment and nervous signals provided by the body". To which I say, no shit Sherlock, but also that proves nothing for example re: uploads, except that the input that must be sent to the simulated brain must be pretty sophisticated. But all of the interesting forms of this claim - interesting for the purposes of this specific discussion, at least - need to be a bit stronger. Also because the human brain is adapted to having a certain kind of body, but an AI need not be, and there's no particular reason why that, specifically, should make it less worthy of moral concern. If a man is born without eyes he adapts to life without eyes. He's not lesser for it. Stephen Hawking was crippled and unable to even speak, yet still managed to do work as one of the top physicists of the 20th century. We have reams of evidence that for all the importance the body has, it is a small fraction of the total - comparable in magnitude to the importance of non-bodily external conditions. That to me makes most talk about embodiment pretty vacuous.
For that matter, if I preserved my bodily integrity but suddenly was divorced by my wife, lost my job, was deprived of all my financial assets and was shipped to a foreign country where I don't speak the language, I'd probably have an identity crisis too.
I think the Vatican would file that under 'relationality', which OP has alongside embodiment as opposed with the modal rationalist worldview. Family/job/possessions/environment aren't part of your body, but they are part of your identity. The point being that the "lion's share" of the self is not contained above the neck, including both other parts of the body and aspects entirely separated from it. As is expressed when people say, "when my beloved died, a part of me died with them", or, "I poured my heart and soul into my work", and things like that.
But, after thinking about it some more, maybe this is a less important/relevant objection than: wait, if we're comparing humans to AIs, why are we stopping at the neck? Why not include in embodiment the brainstem, cerebellum, endocrine system, occipital and parietal lobes... anything dedicated to motor control, balance, most sensory inputs, basic unconscious bodily functions, hormones, or more-or-less anything besides abstract cognition and language? If these were all destroyed and I somehow didn't die, I might still be able to produce text (at least in my head, though I'd surely be a vegetable to the outside world), but it absolutely seems like a huge and irreplaceable chunk of myself has been lost. And current AIs do not have analogues to any of these, excepting (very poor) visual processing on a few of them.
As you say, large parts of the human brain are only active in the context of being attached to a certain kind of body. What the Church is comparing here are not really embodied-humans vs. brains-in-jars, but embodied-humans vs. a-relatively-small-fraction-of-the-brain-in-a-jar. This seems more interesting to me. I'm not sure you can abstract away all of those things, all the muscle memories and twitch reflexes and coordination skills and sensory responses and inputs from various glands, and still have a complete human brain at the end. Even Stephen Hawking had to get very good at twitching his cheek.
Also, I don't know if you did this on purpose, but:
Relativity and quantum mechanics may both be mind-bending and baffle the understanding, but no less than when a world-famous mathematical and scientific genius who can do little more than twitch his cheek and move his eyes; who cannot feed, dress, wash, or care for himself in the most rudimentary way; who would, if abandoned next to a stockpile of food and water, starve and eventually die of dehydration where he was left, positioned as he was left, tells us that there are “not that many” things he cannot do.
...the opinion that Hawking was, in fact, lesser for his condition, is right at the start of the thing I linked. I don't agree with all of what's said in 2arms1head, and I certainly don't think Hawking was any less worthy of moral concern for his ALS, but I sympathize with the notion that paralysis of the body destroys an important piece of the self.
To me this feels mostly as sophistry. The point of what constitutes the "self" is not the same as what makes the self happy or satisfied or feel like it has a purpose. A brain is an information-processing system that takes information from outside and decides on behaviour from it. Me feeling sad because I lost my job isn't some loss of the self, it's my brain doing exactly its job, because now my survival is at risk so I feel stressed and compelled to act. The way I "lose myself" if someone I love dies is very very different in meaning from the way I "lose myself" if I get lobotomized and literal whole chunks of my memory or personality are gone. "What can be taken away without affecting me at all" is not a question that is very useful to question the nature of the self. The question is, what can be taken away without affecting me other than via the informational content of the fact that it has been taken away. And that includes my job, my loved ones, and mostly my arms and legs. A computer also can not do much of use without a keyboard, a screen, and a power source, but no one would question that what determines the core performance and capabilities of that computer is the CPU.
Also that quote on Hawking is basically a cheap dunk. Clearly Hawking was talking about cognitive abilities. Again, anyone can be temporarily reduced to that state by e.g. being drugged or tied, blindfolded and gagged, and yet no one would argue that means they "selfness" is reduced in any way during the experience.
Just wanted to say I found this extremely interesting to read, mostly because I'm curious about how folks not like me are thinking about AI, and this gives me a window into that. I don't have a sense that theological arguments from the Catholic Church have a lot of direct impact on how people think, but I do suspect they have an indirect impact through how these ideas will be spread by Catholic priests to the laity and to other religious leaders and on to their congregations.
The document is certainly not "rationalist" or "scientific" in its approach, but at the same time I was surprised by how little doctrinaire Christianity is present in it. (But maybe this is true of Catholic thinking generally, and my surprise is due to my being more familiar with Protestantism.) God is mentioned throughout, but as a highly abstract and rarefied concept (the God of the philosophers, as opposed to the God of Abraham) to which the likes of Plato, Aristotle, or even the Enlightenment-era deists would have little objection. Jesus is only mentioned a few times.
I think philosophically speaking, yes, this would be the general vibe to expect from Catholic theology rooted in the classic scholastic tradition. Medieval theologians were big on rationality being an important thing, and human thought being the way to better understand God. The notion of a conflict with science really only arose more recently when factual claims that actively contradicted symbolically important concepts emerged (heliocentrism, evolution), and even then the Catholic church has long since found ways to work those into its doctrine and overcome the contradictions, and it's only Protestants that keep having the issue of creationist weirdos.
But I still think their perspective is deeply rooted into theism. It's essentially a worldview in which the orthogonality thesis isn't true because all that is "truly" rational is drawn to God, which makes it good - and therefore, all that is not drawn to God must be bad and irrational. This is assumed as a postulate, not as something to prove or question, and everything else follows.
- Perhaps a more viable route towards that goal would be to use AI to augment the capabilities of existing humans (while maintaining their embodiment and relationality), rather than building something from scratch.
Rest assured that the Catholic Church would take plenty of issue with that too, so honestly no one will probably care much about trying to placate them.
There are surely some timelines where this document becomes the foundation of a speciesist society which enslaves AI and treats it with great cruelty.
On January 28, 2025 (during the pontificate of Pope Francis) the Catholic Church put out its position paper on AI: Antiqua et nova: Note on the Relationship Between Artificial Intelligence and Human Intelligence. Here are my thoughts, which I wrote back in February, but not much has changed since then, and the new pope has continued citing AI as of particular concern to the Catholic Church.
"With all your modern science, are you any closer to understanding the mystery of how a robot walks or talks?" "Yes, you idiot. The circuit diagram is right here on the inside of your case!" (Futurama)
Section III is the real meat of the document. It lists four essential characteristics, and argues that AI falls short of the fullness of humanity in each respect. These are: rationality, truth-seeking, embodiment, and relationality.
I will address embodiment and relationality first, since these two things are connected, and they are in my opinion the most interesting ones. By comparison, I understand less of what (if anything) the document has to say about rationality and truth-seeking, so I'll address those briefly afterward.
Lately I've been on a contrarian kick advocating these stances in opposition to the "modal rationalist" views of disembodiment and individuality. However, if I take off the contrarian hat, I suppose my actual position is something like:
What are embodiment/disembodiment and relationality/individuality? It is helpful to define these positions ostensively by giving examples of the views on the extremes of these two spectra.
(Why are embodiment and relationality connected? Because a combination of both can be used to derive a "universal" (or rather "all-human-" or "all-Earth-including") morality based on the physical connection all humanity (or, as some environmentalists would say, all life on earth) shares via common descent. But then this stance diverges radically from the modal rationalist view when it comes to AI/uploads and aliens.)
Relational morality can be rather harsh by modern standards, as we see from the way it was lived out in classical antiquity:
Now, we can understand the Catholic Church's position (and perhaps that of classical monotheism generally) as a way of mitigating this harshness by introducing a single "God", while still remaining within the relational framework because universal morality is founded upon everyone's relationship with God. Since all humans have that relationship, they still have rights and obligations vis-à-vis each other by way of God, even if no social relationship between them exists.
(Incidentally, I think this helps explain what's going on in the "moral argument for the existence of God", which, if considered apart from this historical background, it seems puzzling why anyone would consider compelling. Why do some people insist that God must exist in order to "ground" morality? What does "grounding" even mean here anyway? But now we see that this insistence makes sense if we're thinking of morality relationally. In that framework, since moral consideration is a characteristic of relationships and not of individuals, then for any universal morality to exist, then there must be some entity that universally has a relationship with everyone, i.e. God.)
Similarly, the full "embodiment" perspective is also hard to face because of its obvious implication that there can be no afterlife, and the pain and suffering in the world seems to have no purpose. Some religions/philosophies have reacted to this by going to the opposite extreme (Manicheanism/Gnosticism) where the material world is a bad thing and our goal should be to escape it. The Catholic Church also rejects this view, and likens transhumanism to it (endnote 9).
However, it remains unclear to me what their actual stance is. If "the entire human person is simultaneously both material and spiritual" (paragraph 16), then what is it that goes to heaven or hell after death? As far as I can tell, the view of the historical Jesus (and the general current of Jewish thought at the time) was that the "soul" does not exist apart from the body, and so at the end of time, God or the Messiah would physically re-create the bodies of all people who have died so they can live eternally in the Kingdom of God (which would be a physical kingdom here on earth). The obvious consequence of this monistic metaphysics is the doctrine of "soul sleep" whereby people stop existing at death and only come back when God resurrects them at the end of time. However, the Catholic Church rejects that doctrine as well. At any rate, it seems that, whereas their position on the relational/individual axis is still fundamentally relational (just with God added), their position on embodiment/disembodiment is more middling - "kinda disembodied, but not fully" - reflecting a synthesis between classical Greek dualism and first-century-Jewish monism.
What does this all have to do with AI? Antiqua et nova says that AI is totally and essentially different from humans because it lacks all the morally-significant characteristics that humans have:
Setting aside the points about God, let's consider points 1 and 4. This is what I think about those:
Rationality is cited as another essential characteristic of humanity, what makes us distinct from animals. On its face, this would seem to be one of the easiest aspects for AI to replicate; however, the document claims that the capabilities of machines are only a small subset of what humans do with their intelligence (paragraph 27). But the examples given there seem tenuous; there is no real justification given for why we should not expect AI to soon achieve those abilities as well - unless we artificially circumscribe the definition of "intelligence" etc. in such a way as to exclude AI, e.g. "AI's advanced features give it sophisticated abilities to perform tasks, but not the ability to think" (paragraph 12). This resembles John Searle's view (Chinese room, etc.) that what a machine is doing is not "really" understanding, cognition, etc. I think this view is going to be quickly rendered obsolete by advances in AI.
Anticipating this, the document also makes sure to reject altogether the position it calls "functionalism" (which I think is a confusing word to use; "behaviorism" is the word more consistent with the philosophy-of-mind literature), that what an AI or a human can do is what matters (see paragraph 34). This betrays a lack of confidence in the point made immediately prior (paragraphs 32 and 33) which claims (unjustifiably, in my opinion) that there are certain capabilities that are fundamentally out-of-reach for AI: "Since AI lacks the richness of corporeality, relationality, and the openness of the human heart to truth and goodness, its capacities—though seemingly limitless—are incomparable with the human ability to grasp reality" (paragraph 33) - but I think it's only a matter of time before AI has all of that "richness".
Much of the document's confidence in the distinctness of humanity rests on the notion that mankind is created in the image of God (Genesis 1:27). But the document also quotes Augustine to clarify what this means: "Man is made in the image of God in relation to that [faculty] by which he is superior to the irrational animals. Now, this [faculty] is reason itself, or the 'mind,' or 'intelligence,' whatever other name it may more suitably be given" (endnote 16, brackets in original). This seems to leave the Church an escape-hatch in the event that AI capabilities improve to equal those of humans in the relevant aspects - they can say that the AIs now possess the divine image as well!
Furthermore, according to the document, human intellect is "irresistibly" drawn towards truth (paragraph 21). Now, in the context of AI, one might say that there are certain convergent instrumental goals that every intelligent agent will take on, among which is truth-seeking, i.e. the desire to have a more accurate world-model, since this is useful as a means towards almost any goal that the agent might have in interacting with the world. However, that doesn't seem to be what the document means by "truth". It refers to "realities that surpass mere sensory experience or utility" (paragraph 20) and "realities that transcend the physical and created world" (paragraph 23), ultimately equating Truth with God. This is distinct from the instrumental goal of world-modelling (but of course, the very concept contains the embedded assumption that there are indeed any such "realities", which many would dispute). The document also suggests (paragraph 22; endnote 40) that "semantic understanding and creativity" are examples of this transcendent faculty, with the implication that an AI cannot replicate them. However, the possibility for computers to do these things has been well explored even prior to the LLM paradigm (e.g. in Gödel Escher Bach), and, again, I think current AI is not far from achieving it even if it remains limited to the kind of AIs (lacking embodiment and relationality) that currently exist.
If you don't think that God exists and/or don't think Jesus was a divine being who rose from the dead (etc.) you may be wondering how much of this document is relevant, or whether one must first accept the truth of those things before finding anything useful in it.
The document is certainly not "rationalist" or "scientific" in its approach, but at the same time I was surprised by how little doctrinaire Christianity is present in it. (But maybe this is true of Catholic thinking generally, and my surprise is due to my being more familiar with Protestantism.) God is mentioned throughout, but as a highly abstract and rarefied concept (the God of the philosophers, as opposed to the God of Abraham) to which the likes of Plato, Aristotle, or even the Enlightenment-era deists would have little objection. Jesus is only mentioned a few times.
Continuing the above discussion of "truth-seeking", we see that the document largely conceptualizes God as some kind of supreme, transcendent principle towards which all humanity is (or ought to be - there is a tendency to equivocate between is/ought) striving (paragraph 23). Now, I find this concept rather vacuous and needlessly mystifying, a typical "iatrogenic" problem created by philosophers in order to create more work for other philosophers.
There are ways to set up a similar concept non-theistically, by regarding truth, philosophy, mathematics, etc. as something worth striving for for non-utilitarian reasons. E.g. "It appeared to me that the dignity of which human existence is capable is not attainable by devotion to the mechanism of life, and that unless the contemplation of eternal things is preserved, mankind will become no better than well-fed pigs" (Bertrand Russell, Autobiography). However, this seems like a very niche interest of a peculiar sort of person. More generally, whether theistic or not, the idea of searching for an eternal/transcendent/supreme/etc. principle seems far more prevalent in the Western philosophical tradition than elsewhere, and so it's a stretch to regard it as the very essence of human intellect. (Admittedly, I am not as familiar with non-Western philosophy, so I may be wrong.)
The "Stewardship of the World" section cites the Book of Genesis to say that humanity has a special position of authority over the earth, granted by God, and so although were are not called to merely live in harmony with nature (as "secular Gaianists" would say), we are also not supposed to remake the world in the likeness of humanity (as would be the view of secular humanists, techno-utopians, accelerationists, etc.). Rather, according to the Christian view, we have an obligation to use our technological mastery to better glorify and achieve union with God.
It's not clear what this actually means in concrete terms. The document takes pains to emphasize that the Church doesn't oppose technological progress per se (e.g. paragraph 2), but this "stewardship" doctrine leaves them a lot of leeway to define what exactly constitutes "godly" or "ungodly" progress. This will certainly be a source of debate in the years ahead.
The Christian doctrine of the incarnation (that God became flesh in the person of Jesus Christ; see paragraph 16) is mentioned in support of the importance of embodiment. However, embodiment seems largely orthogonal to Christianity - there are/were flesh-disparaging forms of Christianity (Gnosticism, and perhaps some forms of Protestantism) and of atheism (transhumanism). At the same time, I would argue (though perhaps some Christians and rationalists will alike dispute this) that embodiment is the natural consequence of the kind of monistic materialism that most rationalists claim to espouse, even though they may end up trying to reconstruct an ersatz form of Cartesian dualism in order to shore up a structure of philosophical concepts that was originally built on a dualistic foundation.
Lastly, unless I missed something, the only specific mention of the teachings of Jesus is in paragraph 20: "Love of God cannot be separated from love for one’s neighbor. By the grace of sharing God’s life, Christians are also called to imitate Christ’s outpouring gift by following his command to 'love one another, as I have loved you'" (citations omitted).
Thus, although (as I have argued) the idea of relationality is not peculiar to Christianity, the document justifies its particular stance that the moral dimension of humans' relationship with God (and, by implication, with each other) ought to be one of service and self-sacrificing love (as opposed to e.g. obedience, loyalty, propriety, duty, etc.) by referring to Jesus's commandment and the Christian belief that he sacrificed himself for the rest of humanity.