In fantasy fiction, we often see that disembodied minds or souls can think just as if they were alive - eg in an afterlife or as incorporeal undead.

In the real world, thinking and other mental activity depends on the brain (as well as a system of glands and hormones, I believe). It is well known that damage to the brain or surgery such as lobotomy can affect the mind and its ability to think.

If disembodied minds can think, then what do they need brains for? In such a world, should brain damage still be a thing?

When I realised this, I decided that in my fictional world, disembodied minds cannot think. Souls do exist and can exist without a body, but without a living brain a soul cannot reason. It is in a dreamlike state of very limited consciousness. The soul does have senses beyond those of the body and can form vague, hazy memories of its experiences in this "afterlife" state, but it needs to be bound to a new body with a brain or the equivalent before it can think again and reflect on its memories (and the "incarnation" process may destroy some of the memories).

What about your fantasy world? If disembodied minds or souls can think, then what do they need brains for? Does brain damage also damage the soul, or does the soul regain full functionality when freed of its fleshly prison? Is a brain a limitation? If so, why have brains?

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    $\begingroup$ Turns out, Aristotle was right and the main function of the brain is to cool the blood. $\endgroup$
    – AlexP
    Dec 31, 2020 at 15:18
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    $\begingroup$ Interesting conundrum. However, It looks like you aren't actually after a solution to a problem but rather a discussion. $\endgroup$ Dec 31, 2020 at 17:23
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    $\begingroup$ The brain amuses itself by posting this question on the Internet. $\endgroup$
    – PcMan
    Dec 31, 2020 at 20:47
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    $\begingroup$ The soul is housed in the brain and gives it extra computing power (extra CPU if you will) $\endgroup$
    – user80981
    Jan 1, 2021 at 4:51
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    $\begingroup$ Try to phrase your question more in terms of "How can I solve this problem" or "How can I make this make sense". This isn't really the right platform for "What did / would you do" discussion type of question. This might just involve removing or rephrasing one or two sentences such as "What about your fantasy world". Something like "Does brain damage also damage the soul" is probably just something any given world builder can decide for themselves and doesn't really have an objective answer. $\endgroup$
    – NotThatGuy
    Jan 1, 2021 at 12:28

9 Answers 9


It’s a metaphysical anchor.

The soul is nice and all, but another name for ‘free-floating soul’ is ‘ghost’. Ghosts are subject to all manner of metaphysical problems (tunnels of light, Valkyrie doing the rounds, Grim Reapers of various forms, wraiths eating the newly departed soul etc. etc.) and as such are highly vulnerable. A brain acts like an anchor, or a storm shelter, keeping the souls firmly in place and protected from the various nasties of the other side. While thus anchored the spirit experiences the sensation of being corporeal. In reality it’s just moving around inside the brain, which happens to be kept functioning by a corporeal body.

If the brain is damaged, some measure of the protection it offers is lost. This means any number of Spiritual Nasties are free to take a bite out of the now vulnerable (but still tethered) spirit. In many ways it’s better for a spirit to just abandon its brain altogether and seek other havens (or heavens), which ends up with brain death. If the spirit clings on, then it can have all manner of chunks taken out of it by various supernatural predators, which could lead to greatly reduced or altered function in a number of ways.

If the body dies, and the brain stops working, then the spirit has no choice: It must flee. If it gets to another receptive brain in time (a newborn, perhaps) it gets another shot at life, though its memories will likely be scrambled by the transfer. If it makes it to an afterlife then it might be afforded some measure of protection by whatever gods/angels are there. If it’s hardy enough (perhaps due to being a Nasty Ghost) or has some other kind of spiritual protection like a totem, freshly reanimated corpse or a particularly well-lived-in house, it might be able to hang on in the real world for a while with no brain to support it.

So basically a Brain is a shelter. Which explains why so many necromancers like putting spirits into skulls.

They find it homely.

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    $\begingroup$ I love this explanation! Especially the part about how brain damage is only bad BEC it tends to lead to soul damage. That's a great idea. I might take some inspiration from this. $\endgroup$ Jan 1, 2021 at 11:44

The brain is a bridge. Notoriously, ghosts can't interact well with the material world. They pass through walls, they can't dig up the chests of stolen gold that are holding them to this plane, they can't move back the boundary stone they had dishonestly shifted, etc.

The brain allows the spirit to link up to the world.

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    $\begingroup$ So the brain is a set of handles to control the body, which can affect the physical world. Without that, the mind/soul has no effect on the physical. ? $\endgroup$
    – Criggie
    Jan 3, 2021 at 5:44

The brain is like a radio. A single human consciousness (a.k.a. a soul) is far too vast and complex to exist in a three pound blob of grey goo. The size of the actual hardware on which we each run is unknown but can be assumed to be enormous.

That soul machine communicates with its dedicated brain through something like radio waves but the nature of those "thought waves" only interacts with our reality within brains. Thought waves are therefore invisible to scientific observation since the only scientists who even see them are neurologists who are so dedicated to proving that the brain is the source of consciousness, that they consider any alternative explanation to be religious/superstitious nonsense.

What processing power is actually resident in the brain is mostly dedicated to encryption, ensuring privacy between each soul and its body.

The brain is therefore a two-directional radio transceiver, constantly connecting the corporeal avatars (which we call bodies) to the soul which resides in an elsewhere far beyond.

As for disembodied souls not being able to think, this could be a matter of context. A soul may be capable of an enormous spectrum of consciousness, but the aspect of that capability which we call thought, the aspect which has context for a linear corporeal reality, requires a connection to that reality. Without the brain, the soul has no understanding of time or causality, so the way that it functions when not attached to a brain cannot be recognized as identity or memory or thought. It still is and still functions on many levels, but none of those remaining levels is anything like what we perceive as life.

  • $\begingroup$ Alternative explanation: much of the brain is dedicated to signal compression. This would explain why different areas of the brain "activate" during different activities. This is essentially the same as my answer, though. $\endgroup$
    – Matthew
    Jan 1, 2021 at 15:16
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    $\begingroup$ @Matthew, you are absolutely right that my answer is similar to yours. Sorry about that. I have upvoted your answer to partially compensate for the inadvertent theft. As it turns out, we both borrowed our answers from the same source material. I was specifically thinking about Card's Children of the Mind as I wrote my answer. I have added your recommended fanfic to my reading list. Thanks! I particularly like your inference that the brain limits the soul down to a level where it needs memory to function. Clearly justifies our lack of pre-life memories. Great stuff! $\endgroup$ Jan 1, 2021 at 16:45
  • $\begingroup$ S'ok, not upset, just "observing"... $\endgroup$
    – Matthew
    Jan 1, 2021 at 17:30

The soul is like the CPU. The brain is like the motherboard. The eyes/ears/etc. are like peripherals.

The soul may be the seat of consciousness, but a CPU will not function well if the RAM is not working properly, or if the signals it's getting from the webcam are scrambled.

It's true we observe personality changes if the brain is damaged, but it's harder to say if this is because the soul is somehow also damaged, or if what we see is fallout from the damage to the interface between the soul and the physical world. Personality is shaped by experience, and what a soul experiences is shaped by any number of environmental factors, including hormones, drugs, and physical injury.

I decided that in my fictional world, disembodied minds cannot think.

I think this is fine if that's the way you want to go. An alternative take would be that disembodied souls either don't interact with the physical world at all (Christian perspective), or interact in some totally alternate way that doesn't need a brain.

It could also be that a soul is normally capable of thinking by itself, but trying to think with a damaged brain is like trying to think in a room with loud noises and obnoxiously flashing lights; too many distractions. Alternatively, maybe they experience time in a totally different manner, such that from its perspective, a disembodied soul can think just fine, but trying to "map" that into our physical reality falls apart somehow without the help of a brain to "mediate".

The soul does have senses beyond those of the body and can form vague, hazy memories of its experiences in this "afterlife" state, but it needs to be bound to a new body with a brain or the equivalent before it can think again and reflect on its memories (and the "incarnation" process may destroy some of the memories).

Again, I could see going whatever direction you want. Maybe a disembodied soul experiences time differently, and so doesn't need "memories" pe se (like in this question). Once tied to a body, however, it relies on the brain for memory storage and retrieval, and so has no knowledge of extra-corporeal existence or (if reincarnation is a thing in your setting) past lives.

It's worth noting I've seen a number of settings where humans have this limitation but some other species does not, and members of that species do retain memories from past lives.

What about your fantasy world?

Fantasy world? This question applies equally to the real world. We still don't understand how consciousness works. Who's to say that you or I don't have souls? Plenty of people still believe that we do.

Does brain damage also damage the soul, or does the soul regain full functionality when freed of its fleshly prison?

Who can say? For your fictional world, I think you could take whichever answer you prefer and run with it.

why have brains?

Why have a motherboard in a computer? The brain is the interface between the body and the soul. Without the brain, the soul would have no senses, no way to control the body. We see this clearly in the case of brain damage, or even just age.

p.s. I cannot recommend strongly enough reading HPatMoR, not just because it's an excellent fanfic, but because it asks exactly this question and comes to the opposite conclusion. (As it happens, I disagree with its conclusion.) For an alternate take, I recommend the Ender's Game series, especially the later books. (I'd read Ender's Game, Speaker for the Dead, Xenocide... and I don't recall if the Card's revealed the juicy bits by then or if you have to read Children of the Mind also. Although Ender in Exile technically happens in between those, it was published later, so in theory won't mess with the arc too much if you skip it.)

p.p.s. You might want to also ask this on Philosophy.SE.

  • $\begingroup$ Who's to say that you or I don't have souls? - Neuroscientists. $\endgroup$
    – forest
    Jan 2, 2021 at 4:06

You can prove a program correct and determine what it will do without running it on a computer or other hardware. Running it on a computer ties its effects to particular input/output devices.

When I rent a cloud server, I can run programs on it. I can hibernate the server and create an image. I can transfer this image to other servers and let it resume there.

What the program does and which state the image reflects is sort of orthogonal to the actual hardware it is running on.

This is of course less accurate with the mind/brain analogy since a brain is plastic: it changes in support of and as a result of the mind's activities.

But you still need a brain to tie a mind to a particular reality.


There's a controversial hypothesis called bicameralism. The rough idea is that, up until about 3000 year ago, people's minds were psychologically split into two pieces: a "part that did" and a "part that directed". The "part that directed" came across as a mental voice ("the voice of god" if you will) and the "part that did" didn't question this (and lacked the capacity to do so), it followed orders.

If we introduce souls to that idea, the soul would be the "part that directed" and the brain would be the "part that did".

The whole concept strikes me as like driving a self-driving car: You (the soul) give the car (the brain) a destination (an objective) and the car (brain) figures out the details of how to accomplish it, which bits to move and how, even having macros (muscle memory) for common tasks.

So, why would a body have a brain in your scenario? To handle the minutiae of running a body and to convert directives into actions.


Remember that non-thinking animals still have brains, or at least cerebral ganglia (other than ctenophores and sponges, which are so simple they don't even have central nervous systems).

If for no other reason, you need a brain because it controls bodily functions, and not just conscious functions like fine motor control. Consider that some animals have multiple brains, in order to distribute control of limbs. One of those is the octopus, which given its intelligence probably has some level of self awareness and a single personality, which means the limb brains are not the ones doing any conscious thinking. Some disembodied entity would have no need of a means of controlling bodily functions, so if that's all the brain is being used for, it wouldn't need a brain.

  • $\begingroup$ "Remember that non-thinking animals still have brains" - but they don't. $\endgroup$
    – Ivana
    Jan 3, 2021 at 18:16

The soul is simply an observer

The body goes its own way and does its own thing according to the laws of physics. It is an automaton. God does not watch humans from outside, he watches from inside using parallel-processing. Souls do not exist as such, they are a part of God's consciousness - the consciousness of the universe. God is the universe and souls allow the universe to observe itself from within.

Imagine someone watching millions of TV sets at once (rather like security monitors in a large building). If one set dies, the observer remains the same. As long as one TV remains, there is something to watch.

When a body dies, it's no different from, say, a TV breaking. God no longer has a way of observing anything in the physical world through that particular mechanism.

  • $\begingroup$ The question was specifically about fictional fantasy worlds in which disembodied souls CAN do stuff. $\endgroup$ Jan 1, 2021 at 20:46
  • $\begingroup$ @Claus Appel - Please quote where it says they can do stuff. I can't see anything in the OP where it states that (apart from simply being aware). A security guard can be aware even if s/he is not watching the monitors. $\endgroup$ Jan 1, 2021 at 20:48

Suppose that I have a program running on a modern CPU. Let us suppose that I also have a way of running programs through some much more advanced mechanism: say, some hypothetical sophisticated computer that runs on photons. Suppose my technology is so advanced that I do not even need solids to confine the photons, but I can use gas or plasma or EM fields or whatever. Now, I can couple those two systems, so that the programs are running on the CPU, but if they need to use the resources of my super-advanced light computer, they can reach out and execute instructions on that computer instead.

Now suppose that I go one step further. I have the system set up so that if the conventional computer degrades too much to continue running its programs, those programs will be transferred in a rapid and completely continuous1 fashion to the trapped light computer. Thus we do not need to be overly concerned about whether it is still the same operating system, since there is no sharp transition point between when it stops running on the conventional machine and starts running on the light computer. Since I am building the system, I get to determine its behavior, and I say that merely damaging it without rendering it incapable of running will not trigger the transfer.

  • Why not just use the optical computer? I am the system designer, and I like conventional computers, so I can do whatever I want. The optical computer is there because I want my system to be robust if the conventional computer fails. Maybe the conventional computer was created by a completely different process, or even by extraordinary random chance and the accumulation of useful innovations, and I am just adding something on. Also, maybe it is slower, like real-life optical computers in 2020, so that the programs are limited in their ability to evolve once they have fully transferred over. This might also mean that to a program on the optical computer, centuries could seem like the blink of an eye.

  • Does damaging the CPU also damage the optical computer? Not usually, since the systems are fairly isolated except in exceptional circumstances. Still, maybe there is some powerful electric surge or something similar that would overwhelm those protections and damage the optical computer as well.

Please feel free to replace the conventional computer with a human brain, the optical computer with a soul, and make any other appropriate substitutions.

1: At least from a macroscopic perspective.


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