The metaphysics of head and brain transplants

Besides, I was always told that two heads were better than one. So, by comparison, settling for a one-for-one trade wouldn’t be nearly as advantageous.


Could you explain a bit further how you see Dennett as a dualist?

The understanding of the “self” that makes the most sense to me is that at every moment of time the molecules of our body are configured such that we have memories of previous experiences, from the beginning of our life to the last moment. This is why we have the sense of a stable sense moving thru time and space. In effect, every moment of our existence is Last Thursday, and we operate as if we have a stable self for the same reasons that we assume the world was not suddenly created last Thursday with the appearance of being 14 billion years old.

Under this understanding it would be expected that Tom’s self would continue to exist if his brain was transplanted to Dick’s body, because the brain’s physical parameters would still encode the same information they did when in Tom’s body.

This would be an outcome similar to what Egnor imagines happening if his neighbour’s right eye and brain was transplanted into his head. However, I don’t really understand why he assumes this. Why would the neighbour’s soul remain attached to his brain? Why would Egnor’s soul not, instead, latch onto the neighbour’s brain once the brain is in Egnor’s skull and continue using it just as if it had been Egnor’s brain all along?

It’s hard to be specific here. It has to do with the way that Dennett sees his relation to the world. And, based on your post – the one to which I am replying, I would have to conclude that you are also a dualist, though I expect you to be in denial about that.

Both of you see your relation to the world in a way that is very compatible with dualism (and with Berkeley’s idealism), but that seems not at all compatible with being a biological organism.

Dennett denies a self. I deny the possibility of recording memories (except with the recording technology that we have created).

You say “from the beginning of life”. But our memories do not go back that far. I believe this is called “childhood amnesia” or “infantile amnesia”.

The best (if imperfect) analogy that I can think of, is a tuning fork. Let’s say I have a tuning fork for middle C. We can talk of it having a memory. But it hasn’t really remembered anything. Rather, there is a kind of resonance.

I see the brain as tuning itself to fit with the world. So it adjusts itself to resonate with some experiences. Memories are not recordings, but are reconstruction based on stimulating some of those resonances. We have no memory of early childhood, because the resonances did not exist that early in life.

A clock can be said to have a stable sense of moving through time. And a ruler can be said to have a stable sense of space. They can be said to have a stable sense of time and space because they are our standards for measuring time and space.

We can have a stable sense of time and space, because our brains are themselves implementing some kind of standard by which we judge time and space. But those standards are physical, even if we don’t know the physical details of implementation. If there were no physical implementation, then there would be no reason to expect our judgements of time and space to be stable. As I see it, my self is embodied in the physical standards that I am using when I make perceptual judgements about the world.

There’s a really big difference in how we look at things.

As far as I am concerned, information does not actually exist. The word “information” refers to an abstraction, which we treat as a useful fiction.

A cat walks in front of a child.

A dandelion seed head wafts in front of the child. Aha, another cat?

The only way that the child can tell that the dandelion head is not a cat, is if he has some standard for what he will consider to be a cat. In order to be able to perceive a world, we have to develop our own standards. A young child cannot take the community standards, because that young child has not yet acquired the ability to perceive a community. So a young child needs to start by inventing his own standards that he can use to perceive his world. Information can only exist relative to the standards used.

If my head is transplanted to Tom’s body, what standard will it use to perceive. Maybe my standard for judging length comes from the length of my index finger or from the distance between my eyes. But those will be different for Tom’s body. So the brain has lost its way. It cannot get information until it creates new standards.

Step into our surgery, and we can fix that for you. :wink:

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Interestingly put, @nwrickert . I think I may be largely in agreement with you on all of that. It seems to me that one of the most common errors we make in our thinking is to assume that the things, concepts and phenomena which we experience or consider are “real” things as opposed to being explanatory abstractions that happen to be quite useful to us as organisms. It doesn’t mean reasoning is futile, but it does mean that it has to be done with a degree of caution.

Science works well in part because we do make an effort, in most fields, to drill down to something that may closely represent what is actually going on. Philosophy can work very poorly at times because we reify great big concepts and try to apply rules to these – but they are big squishy abstractions and cannot always be made to fit, even roughly, into a system of reasoning. I therefore fall asleep whenever a theologian announces that this and that is what we know about, say, “atonement.” In the law, we have no choice but to reason about big puffy abstractions, like “contracts” and “rights,” because the questions we need to answer are answerable in no other terms; but even in the law we do have a few empirical tie-downs, bungee cords that keep our abstractions from getting too terribly out of touch with boots-on-the-ground facts. In theology, all the tiedowns are gone.

That digresion, admittedly, has little to do with dualism and less to do with brain surgery, of either the competent or Egnorant varieties. But there it is.


Yes, this.

Our explanatory abstractions work quite well, mainly because we are pragmatists. All biological organisms are pragmatists to some degree. Natural selection is a filter which favors pragmatism.

So when our society comes up with a better system of abstractions, then we prefer those – unless we are too strongly tied to a theology which rejects those better systems.

Another common mistake is to overrate logic. Logic is fine, but the tendency is to give it too much credit.

When we have a problem, we construct a logical model, and then use that model to solve the problem. There is a tendency to give the credit for this to logic, whereas the main credit should go to the creativity of model making.


On that, I couldn’t count the number of times I have been presented by a creationist with some horribly flawed attempt at a syllogism. When I attempt to explain what is the matter with that syllogism, I am met with “so, you don’t believe in logic, then!” Likewise, one will explain what’s wrong with Douglas Axe’s numbers, and be told that this is denying the math. It’s hard for people to wrap their heads around the possibility that the math may be unimpeachable AS MATH, but that if the mathematical model itself poorly represents the external world, its internal mathematical soundness is all for nothing.

I think that the excessive faith in “logic” which you refer to has something to do with the nature of a lot of creationist “arguments.” The inability of “arguments,” in the air so to speak, to resolve much seems often to be lost on them. They underestimate the power of data in comparison to pure abstract reasoning. Which, of course, is not to say they’re very good at the latter, either.

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It occurs to me that the more frequently we use a given set of “explanatory abstractions” in our every day life (professional, spiritual, etc), the more prone we are to forget that they are abstractions and treat them as “real”.

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I don’t know if our positions are actually that far apart. For my part, I believe it possible that many aspects that appear to us to inhere in the outside world, such as causation, logic, time, etc, are actually computational processes of our brain that exist to allow us to survive in the environment in which they evolved. If the tape of time was rewound, it is possible that some other organism would have evolved with cognitive systems that are similarly complex, but operate completely differently without these concepts.

That said, I am not sure how you are using the term “dualism”. At the risk of oversimplification, I tend to try translate such abstract metaphysical concepts into terms that could be tested empirically, at least in principle. So I understand dualism to entail that the functioning of our minds cannot be completely accounted for by the the laws of physics and chemistry as we currently understand them.

This can be further subdivided into property dualism, under which a proper account would require that we identify new attributes of the physical world in addition to the ones of which we already know such as mass, energy, charge, forces, etc. These new concepts, however, could be subsumed within and expand our existing theories and models of physics. Substance dualism, OTOH, is the position that we need to identify an entirely new ontological category of processes and entities to which the very concept of physical laws does not even apply.

Is that consistent with your understanding, or do you have a different one?

I also do not understand why the functioning of a brain should be any more affected by transplantation than is a heart or a kidney. To be sure, if Tom was a marathon runner with 20/20 vision, it might be discomfiting to his brain when it finds itself in the body of Dick who is a near-sighted couch potato. But as far as the functions that are confined to the brain alone, I don’t see why these should be changed such that the sense of self is lost.

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While all simplifications are wrong at some level, in the frame of Kahneman’s fast and slow thinking, it appears to me that creationists misrepresent their fast thinking as slow thinking, both to themselves and to others.

One fascinating thing that has surprised me is that both @jeffb and @thoughtful have admitted that they don’t understand the concept of the nested hierarchy, which looks to me like a defensive move that doesn’t fit the fast/slow dichotomy.

I see it as more of a desperate refusal to accept the preeminence of data. It’s as though they know, at least on some level, that their arguments will fall apart.


They are very far apart.

By contrast, I seriously doubt that there are any computational processes in the brain.

Yes, we do computation, and use our brains to do that. We could say the brain is doing computation when we do. But if you could look more closely, I don’t think you would see activity that resembled what we would call “computation”. It might resemble moving beads on an abacus, but without the intentions needed for that to count as computation.

I can go with that. But the way I would then put it, is that the functioning of our minds cannot be accounted for with computational models.

I should note that I take “mind” to be a metaphor. We cannot actually locate anything that matches peoples ideas of a mind. So when we talk of “functioning of our minds” we are talking about things that minds are said to be able to do. That’s not at all the same as talking about the biological functioning of the brain. I’m inclined to say that physics and chemistry give a pretty good account of that biological functioning.

I’m doubting that there are many such functions. I see brain as intimately engaged in almost everything that happens in our bodies.

Yes, very much so! I have had to express to them so very many times the notion that while a sort of loosely intuitive mode of thought may be a great starting point for, say, hypothesis formation, it really stinks as a way of working out a problem well. What’s funny is that they will “see” that when it suits their interests: there’s a particular Ernst Mayr quote-mine in which he talks about how paleontological hypotheses require a sort of creative narrative construction, and they’ll point to that and say, “see? It’s all story-telling!” But, of course, Mayr isn’t saying this is how one TESTS a hypothesis, but how one might construct one to be tested.

I’ve been watching that and am a bit baffled, honestly. The nested hierarchy was obvious to Linnaeus, without an evolutionary explanation. I’m not saying everyone should be as clever on this as he was, but I’d have thought it was pretty obvious to everyone. Our colloquial intuitive sorting of animals in our own heads tends to reveal its structure, and then the only further insight required is that deeper analysis of both morphology and genetics further reveals similar structure. What’s to miss?

Heck, as a child I noticed that all mammals had pretty much the same complement of organs. It wasn’t hard to guess why that might be.

Yes, perhaps. The whole thing has a kind of desperation about it. Some of this is just laziness. Data-based thinking is hard, not least because you’ve got to go find the data. So what would be a nice shortcut? Philosophical reasoning that “proves” the impossibility of your opponent’s position would do the trick! The difficulty, of course, is that there aren’t a lot of empirical problems which are amenable to that sort of thing.

And, frankly, a lot of creationists think of the problem primarily as one in philosophy/theology anyhow. They’re used to the idea that people argue about the existence of gods in purely philosophical terms: the “problem of evil” and that sort of thing. They seem, often, to be unfamiliar with the fact that philosophers tend to find all of those god-existence arguments tiresome, well-worn and inconclusive. The feeling is that The Truth has GOT to be accessible to pure reason. And as problems like the existence of gods tend to frustrate empirical inquiry, philosophy may seem like it is superior in some sense – that it isn’t slowed down by the lack of useful data.

Truth, alas, if “truth” is the word for it at all, is not just sitting there waiting for us to think it up. It’s got to be mined.


Oh, is all this why you occasionally say

“x” philosophical concept is absurd”


Or do I have the wrong person? I think that was you.

I may have occasionally said that.

From my perspective, professional philosophers are pretty smart people. But their thinking can become too strongly tied to tradition instead of being tied to evidence.

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I’ll interject here.

Yes, it (science) is all story telling. Thus we have the phlogiston of the gaps, the ether of the gaps.

You can already see the difference. Scientists engage is story telling to make their explanations. But they strenuously test their stories and reject the ones that don’t work.

Story telling, making up explanations – it’s something that humans do. The rigorous testing is what makes science different.


Yes, but I mean the basic set concept itself.

It does suggest a bait-and-switch educational strategy, though; teach students the difference between nested and non-nested hierarchies using designed machines BEFORE presenting the concept in any biological context.

I find yours one of the more intriguing and interesting comments.

Have you ever considered dreams? I always dream, and in my dreams I encounter many different people, dead and alive, that I have met and interacted with in the course of my life. They are very clear, very specific and very life-like. In contrast, the situations I encounter them in are more generic and often quite far-fetched. Actually, come to think of it, I’m not sure I ever encountered someone in my dreams that I had never met in my real life before ( I realise that this doesn’t make me very romantic)

I wonder what it could be that triggers the appearance of these people. What is it during my sleep that evokes such resonances? Why is it that the people are so life-like whereas the situations are so generic and so fictional?

More on-topic, who would someone with a brain transplant be dreaming about?

Beats a civilization of mostly people with their heads in the sand.

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“Intentions.” Hmm. What would that look like, and why would you expect to see it?

For my part, I expect to see nothing other that what could be likened to the movement of beads on an abacus, though a bit more complex.

My best guess is that his dreams would be little different from the dreams the person who originally owned the brain had when the brain was in his body. But, as I say, that’s just a guess. Unless and until someone can actually do brain transplants, we’ll never really know.

Yes, I have.

I rarely remember much about my dreams.

When I try to explain dreaming, I am mostly guessing. But here’s what I think might be happening:

When we have a complex tightly tuned piece of machinery, there’s always a problem that it might get out of tune. To avoid this, there’s an alignment procedure to keep things working about right. In the old days, a radio technician would use a signal generator and then align tuned circuits to the generated signals. And I guess that there are still piano tuners.

My guess is that the brain is generating alignment signals. For example, it needs to adjust things so that what you see with the left eye is consistent with what you see with the right eye. I am suspecting that dreams are a side effect of this alignment procedure.