There’s little if any doubt that the brain (the human brain in particular) is the most complex entity or system that we’ve ever encountered in the known universe, and thus it is not surprising that it has allowed humans to reach the top of the food chain and also the ability to manipulate our environment more than any other creature on Earth. Not only has it provided humans with the necessary means for surviving countless environmental pressures, effectively evolving as a sort of anchor and catalyst for our continued natural selection over time (through learning, language, adaptive technology, etc.), but it has also allowed humans to become aware of themselves, aware of their own consciousness, and aware of their own brains in numerous other ways. The brain appears to be the first evolved feature of an organism capable of mapping the entire organism (including its interaction with the external environment), and it may even be the case that consciousness later evolved as a result of the brain making maps of itself. Even beyond these capabilities, the human brain has also been able to map itself in terms of perceptually acquired patterns related to its own activity (i.e. when we study and learn about how our brains work).
It isn’t at all surprising when people marvel over the complexity, beauty and even seemingly surreal qualities of the brain as it produces the qualia of our subjective experience including all of our sensations, emotions and the resulting feelings that ensue. Some of our human attributes are so seemingly remarkable, that many people have gone so far as to say that at least some of these attributes are either supernatural, supernaturally endowed, and/or are forever exclusive to humans. For example, some religious people claim that humans alone have some kind of immaterial soul that exists outside of our experiential reality. Some also believe that humans alone possess free will, are conscious in some way forever exclusive to humans (some have even argued that consciousness in general is an exclusively human trait), and a host of other (perhaps anthropocentric) “human only” attributes, with many of them forever exclusive to humans. In the interest of philosophical exploration, I’d like to consider and evaluate some of these claims about “exclusively human” attributes. In particular, I’d like to focus on the non-falsifiable claim of having a soul, with the aid of reason and a couple of thought experiments, although these thought experiments may also shed some light on other purported “exclusively human” attributes (e.g. free will, consciousness, etc.). For the purposes of simplicity in these thought experiments, I may periodically refer to many or all purported “humanly exclusive” attributes as simply, “H”. Let’s begin by briefly examining some of the common conceptions of a soul and how it is purported to relate to the physical world.
What is a Soul?
It seems that most people would define a soul to be some incorporeal entity or essence that serves as an immortal aspect or representation of an otherwise mortal/living being. Furthermore, many people think that souls are something possessed by human beings alone. There are also people who ascribe souls to non-living entities (such as bodies of water, celestial bodies, wind, etc.), but regardless of these distinctions, for those that believe in souls, there seems to be something in common: souls appear to be non-physical entities correlated, linked, or somehow attached to a particular physical body or system, and are usually believed to give rise to consciousness, a “life force”, animism, or some power of agency. Additionally, they are often believed to transcend material existence through their involvement in some form of an afterlife. While it is true that souls and any claims about souls are unfalsifiable and thus are excluded from any kind of empirical investigation, let’s examine some commonly held assumptions and claims about souls and see how they hold up to a more critical examination.
Creation or Correlation of Souls
Many religious people now claim that a person’s life begins at conception (after Science discovered this specific stage of reproduction), and thus it would be reasonable to assume that if they have a soul, that soul is effectively created at conception. However, some also believe that all souls have co-existed for the same amount of time (perhaps since the dawn of our universe), and that souls are in some sense waiting to be linked to the physical person once they are conceived or come into existence. Another way of expressing this latter idea is the belief that all souls have existed since some time long ago, but only after the reproductive conception of a person does that soul begin to have a physical correlate or incarnation linked to it. In any case, the presumed soul is believed to be correlated to a particular physical body (generally presumed to be a “living” body, if not a human body), and this living body has been defined by many to begin its life either at conception (i.e. fertilization), shortly thereafter as an embryo (i.e. once the fertilized egg/cell undergoes division at least once), or once it is considered a fetus (depending on the context for such a definition). The easiest definition to use for the purposes of this discussion is to define life to begin at conception (i.e. fertilization).
For one, regardless of the definition chosen, it seems difficult to define exactly when the particular developmental stage in question is reached. Conception could be defined to take place once the spermatozoa’s DNA contents enter the zygote or perhaps not until some threshold has been reached in a particular step of the process afterward (e.g. some time after the individual parent DNA strands have mixed to produce a double-helix daughter strand). Either way, most proponents of the idea of a human soul seem to assume that a soul is created or at least correlated (if created some time earlier) at the moment of, or not long after, fertilization. At this point, the soul is believed to be correlated or representative of the now “living” being (which is of course composed of physical materials).
At a most basic level, one could argue, if we knew exactly when a soul was created/correlated with a particular physical body (e.g. a fertilized egg), then by reversing the last step in the process that instigated the creation/correlation of the soul, we should be able to destroy/decorrelate the soul. Also, if a soul was in fact correlated with an entire fertilized egg, then if we remove even one atom, molecule, etc., would that correlation change? If not, then it would appear that the soul is not actually correlated with the entire fertilized egg, but rather it is correlated with some higher level aspect or property of it (whatever that may be).
Conservation & Identity of Souls
Assuming a soul is in fact created or correlated with a fertilized egg, what would happen in the case of chimerism, where more than one fertilized egg fuse together in the early stages of embryonic development? Would this developing individual have two souls? By the definition or assumptions given earlier, if a soul is correlated with a fertilized egg in some way, and two fertilized eggs (each with their own soul) merge together, then this would indicate one of a few possibilities. Either two souls merged into one (or one is actually destroyed) which would demonstrate that the number of souls are not conserved (indicating that not all souls are eternal/immortal), or the two souls would co-exist with that one individual and would imply that not all individuals have the same number of souls (some have one, some may have more) and thus souls don’t each have their own unique identity with a particular person, or it would indicate that after the merging of fertilized eggs took place, one of the two souls would detach from or become decorrelated with its physical counterpart, and the remaining soul would get to keep the booty of both fertilized eggs or so to speak.
In the case of identical twins, triplets, etc., a fertilized egg eventually splits, and we are left with the opposite conundrum. It would seem that we would be starting with one soul that eventually splits into two or more, and thus there would be another violation of the conservation of the number of souls. Alternatively, if the number of souls are indeed conserved, an additional previously existing soul (if this was the case) could become correlated with the second fertilized egg produced. Yet another possibility would be to say that the “twins to be” (i.e. the fertilized egg prior to splitting) has two souls to start with and when the egg splits, the souls are segregated and each pre-destined twin is given their own.
The only way to avoid these implications would be to modify the assumption given earlier, regarding when a soul is created or correlated. It would have to be defined such that a soul is created or correlated with a physical body some time after an egg is fertilized when it is no longer possible to fuse with another fertilized egg and after it can no longer split into fertilized multiples (i.e. twins, triplets, etc.). If this is true, then one could no longer say that a fertilized egg necessarily has a soul, for that wouldn’t technically be the case until some time afterward when chimerism or monozygotic multiples were no longer possible.
If people believe in non-physical entities that can’t be seen or in any way extrospectively verified, it’s not much of a stretch to say that they can come up with a way to address these questions or reconcile these issues, with yet more unfalsifiable claims. Some of these might not even be issues for various believers but I only mention these potential issues to point out the apparent arbitrariness or poorly defined aspects of many claims and assumptions regarding souls. Now let’s look at a few thought experiments to further analyze the concept of a soul and purported “exclusively human” attributes (i.e. “H”) as mentioned in the introduction of this post.
Conservation and Identity of “H”
Thought Experiment # 1: Replace a Neuron With a Non-Biological Analog
What if one neuron in a person’s brain is replaced with a non-biological/artificial version, that is, what if some kind of silicon-based (or other non-carbon-based) analog to a neuron was effectively used to replace a neuron? We are assuming that this replacement with another version will accomplish the same vital function, that is, the same subjective experience and behavior. This non-biologically-based neuronal analog may be powered by ATP (Adenosine Triphosphate) and also respond to neurotransmitters with electro-chemical sensors — although it wouldn’t necessarily have to be constrained by the same power or signal transmission media (or mechanisms) as long as it produced the same end result (i.e. the same subjective experience and behavior). As long as the synthetic neuronal replacement accomplished the same ends, the attributes of the person (i.e. their identity, their beliefs, their actions, etc.) should be unaffected despite any of these changes to their hardware.
Regarding the soul, if souls do in fact exist and they are not physically connected to the body (although people claim that souls are somehow associated with a particular physical body), then it seems reasonable to assume that changing a part of the physical body should have no effect on an individual’s possession of that soul (or any “H” for that matter), especially if the important attributes of the individual, i.e., their beliefs, thoughts, memories, and subsequent actions, etc., were for all practical purposes (if not completely), the same as before. Even if there were some changes in the important aspects of the individual, say, if there was a slight personality change after some level of brain surgery, could anyone reasonably argue that their presumed soul (or their “H”) was lost as a result? If physical modifications of the body led to the loss of a soul (or of any elements of “H”), then there would be quite a large number of people (and an increasing number at that) who no longer have souls (or “H”) since many people indeed have had various prosthetic modifications used in or on their bodies (including brain and neural prosthetics) as well as other intervening mediation of body/brain processes (e.g. through medication, transplants, various levels of critical life support, etc.).
For those that think that changing the body’s hardware would somehow disconnect the presumed soul from that person’s body (or eliminate other elements of their “H”), they should consider that this assumption is strongly challenged by the fact that many of the atoms in the human body are replaced (some of them several times over) throughout one’s lifetime anyway. Despite this drastic biological “hardware” change, where our material selves are constantly being replaced with new atoms from the food that we eat and the air that we breathe (among other sources), we still manage to maintain our memories and our identity simply because the functional arrangements of the brain cells (i.e. neurons and glial cells) which are composed of those atoms are roughly preserved over time and thus the information contained in such arrangements and/or their resulting processes are preserved over time. We can analogize this important point by thinking about a computer that has had its hardware replaced, albeit in a way that matches or maintains its original physical state, and understand that as a result of this configuration preservation, it also should be able to maintain its original memory, programs and normal functional operation. One could certainly argue that the computer in question is technically no longer the “same” computer because it no longer has any of the original hardware. However, the information regarding the computer’s physical state, that is, the specific configuration and states of parts that allow it to function exactly as it did before the hardware replacement, is preserved. Thus, for all practical purposes in terms of the identity of that computer, it remained the same regardless of the complete hardware change.
This is an important point to consider for those who think that replacing the hardware of the brain (even if limited to a biologically sustained replacement) is either theoretically impossible, or that it would destroy one’s ability to be conscious, to maintain their identity, to maintain their presumed soul, or any presumed element of “H”. The body naturally performs these hardware changes (through metabolism, respiration, excretion, etc.) all the time and thus the concept of changing hardware while maintaining the critical aspects of an individual is thoroughly demonstrated throughout one’s lifetime. On top of this, the physical outer boundary that defines our bodies is also arbitrary in the sense that we exchange atoms between our outer surface and the environment around us (e.g. by shedding skin cells, or through friction, molecular desorption/adsorption/absorption, etc.). The key idea to keep in mind is that these natural hardware changes imply that “we” are not defined specifically by our hardware or some physical boundary with a set number of atoms, but rather “we” are based on how our hardware is arranged/configured (allowing for some variation of configuration states within some finite acceptable range), and the subsequent processes and functions that result from such an arrangement as mediated by the laws of physics.
Is the type of hardware important? It may be true that changing a human’s hardware to a non-biological version may never be able to accomplish exactly the same subjective experience and behavior that was possible with the biological hardware, however we simply don’t know that this is the case. It may be that both the type of hardware as well as the configuration are necessary for a body and brain to produce the same subjective experience and behavior. However, the old adage “there’s more than one way to skin a cat” has been applicable to so many types of technologies and to the means used to accomplish a number of goals. There are a number of different hardware types and configurations that can be used to accomplish a particular task, even if, after changing the hardware the configuration must also be changed to accomplish a comparable result. The question becomes, which parts or aspects of the neural process in the brain produces subjective experience and behavior? If this becomes known, we should be able to learn how biologically-based hardware and its configuration work together in order to accomplish a subjective experience and behavior, and then also learn if non-biologically-based hardware (perhaps with its own particular configuration) can accomplish the same task. For the purposes of this thought experiment, let’s assume that we can swap out the hardware with a different type, even if, in order to preserve the same subjective experience and behavior, the configuration must be significantly different than it was with the original biologically-based hardware.
So, if we assume that we can replace a neuron with an efficacious artificial version, and still maintain our identity, our consciousness, any soul that might be present, or any element of “H” for that matter, then even if we replace two neurons with artificial versions, we should still have the same individual. In fact, even if we replace every neuron, perhaps just one neuron at a time, eventually we would be replacing the entire brain with an artificial version, and yet still have the same individual. This person would now have a completely non-biologically based “brain”. In theory, their identity would be the same, and they would subjectively experience reality and their selves as usual. Having gone this far, let’s assume that we replace the rest of the body with an artificial version. Replacing the rest of the body, one part at a time, should be far less significant a change than replacing the brain, for the rest of the body is far less complex.
It may be true that the body serves as an integral homeostatic frame of reference necessary for establishing some kind of self-object basis of consciousness (e.g. Damasio’s Theory of Consciousness), but as long as our synthetic brain is sending/receiving the appropriate equivalent of sensory/motor information (i.e. through an interoceptive feedback loop among other requirements) from the new artificial body, the model or map of the artificial body’s internal state provided by the synthetic brain should be equivalent. It should also be noted that the range of conditions necessary for homeostasis in one human body versus another is far narrower and less individualized than the differences found between the brains of two different people. This supports the idea that the brain is in fact the most important aspect of our individuality, and thus replacing the rest of the body should be significantly easier to accomplish and also less critical a change. After replacing the rest of the body, we would now have a completely artificial non-biological substrate for our modified “human being”, or what many people would refer to as a “robot”, or a system of “artificial intelligence” with motor capabilities. This thought experiment seems to suggest at least one of several implications:
- Some types of robots can possess “H” (e.g. soul, consciousness, free-will, etc.), and thus “H” are not uniquely human, nor are they forever exclusive to humans.
- Humans lose some or all of their “H” after some threshold of modification has taken place (likely a modification of the brain)
- “H”, as it is commonly defined at least, does not exist
The first implication listed above would likely be roundly rejected by most people that believe in the existence of “H” for several reasons including the fact that most people see robots as fundamentally different than living systems, they see “H” as only applicable to human beings, and they see a clear distinction between robots and human beings (although the claim that these distinctions exist has been theoretically challenged by this thought experiment). The second implication sounds quite implausible (even if we assume that “H” exists) as it would seem to be impossible to define when exactly any elements of “H” were lost based on exceeding some seemingly arbitrary threshold of modification. For example, would the loss of some element of “H” occur only after the last neuron was replaced with an artificial version? If the loss of “H” did occur after some specific number of neurons were removed (or after the number of neurons that remained fell below some critical minimum quantity), then what if the last neuron removed (which caused this critical threshold to be met) was biologically preserved and later re-installed, thus effectively reversing the last neuronal replacement procedure? Would the previously lost “H” then return?
Thought Experiment # 2: Replace a Non-Biological Neuronal Analog With a Real Neuron
We could look at this thought experiment (in terms of the second implication) yet another way by simply reversing the order of the thought experiment. For example, imagine that we made a robot from scratch that was identical to the robot eventually obtained from the aforementioned thought experiment, and then we began to replace its original non-biologically-based neuronal equivalent with actual biologically-based neurons, perhaps even neurons that were each taken from a separate human brain (say, from one or several cadavers) and preserved for such a task. Even after this, consider that we proceed to replace the rest of the robot’s “body”, again piecewise (say, from one or several cadavers), until it was completely biologically-based to match the human being we began with in the initial thought experiment. Would or could this robot acquire “H” at some point, or be considered human? It seems that there would be no biological reason to claim otherwise.
Does “H” exist? If So, What is “H”?
I’m well aware of how silly some of these hypothetical questions and considerations sound, however I find it valuable to follow the reasoning all the way through in order to help illustrate the degree of plausibility of these particular implications, and the plausibility or validity of “H”. In the case of the second implication given previously (that humans lose some or all of “H” after some threshold of modification), if there’s no way to define or know when “H” is lost (or gained), then nobody can ever claim with certainty that an individual has lost their “H”, and thus they would have to assume that all elements of “H” have never been lost (if they want to err on the side of, what some may call, ethical or moral caution). By that rationale, one would find themselves forced to accept the first implication (some types of robots can possess “H”, and thus “H” isn’t unique to humans). If anyone denies the first two implications, it seems that they are only left with the third option. The third implication seems to be the most likely (that “H” as previously defined does not exist), however it should be mentioned that even this third implication may be circumvented by realizing that it has an implicit loophole. There is a possibility that some or all elements and/or aspects of “H” are not exactly what people assume them to be, and therefore “H” may exist in some other sense. For example, what if we considered particular patterns themselves, i.e., the brain/neuronal configurations, patterns of brain waves, neuronal firing patterns, patterns of electro-chemical signals emanated throughout the body, etc., to be the “immaterial soul” of each individual? We could look at these patterns as being immaterial if the physical substrate that employs them is irrelevant, or by simply noting that patterns of physical material states are not physical materials in themselves.
This is analogous to the concept that the information contained in a book can be represented on paper, electronically, in multiple languages, etc., and is not reliant on a specific physical medium. This would mean that one could accept the first implication that robots or “mechanized humans” possess “H”, although it would also necessarily imply that any elements of “H” aren’t actually unique or exclusive to humans as they were initially assumed to be. One could certainly accept this first implication by noting that the patterns of information (or patterns of something if we don’t want to call it information per se) that comprise the individual were conserved throughout the neuronal (or body) replacement in these thought experiments, and thus the essence or identity of the individual (whether “human” or “robot”) was preserved as well.
Pragmatic Considerations & Final Thoughts
I completely acknowledge that in order for this hypothetical neuronal replacement to be truly accurate in reproducing normal neuronal function (even with just one neuron), above and beyond the potential necessity of both a specific type of hardware as well as configuration (as mentioned earlier), the non-biologically based version would presumably also have to replicate the neuronal plasticity that the brain normally possesses. In terms of brain plasticity, there are basically four known factors involved with neuronal change, sometimes referred to as the four R’s: regeneration, reconnection, re-weighting, and rewiring. So clearly, any synthetic neuronal version would likely involve some kind of malleable processing in order to accomplish at least some of these tasks (if not all of them to some degree), as well as some possible nano-self-assembly processes if actual physical rewiring were needed. The details of what and how this would be accomplished will become better known over time as we learn more about the possible neuronal dynamic mechanisms involved (e.g. neural darwinism or other means of neuronal differential reproduction, connectionism, Hebbian learning, DNA instruction, etc.).
I think that the most important thing to gain from these thought experiments is the realization of the inability or severe difficulty in taking the idea of souls or “H” seriously given the incompatibility between the traditional conception of a concrete soul or other “H” and the well-established fluidic or continuous nature of the material substrates that they are purportedly correlated with. That is, all the “things” in this world, including any forms of life (human or not) are constantly undergoing physical transformation and change, and they possess seemingly arbitrary boundaries that are ultimately defined by our own categorical intuitions and subjective perception of reality. In terms of any person’s quest for “H”, if what one is really looking for is some form of constancy, essence, or identity of some kind in any of the things around us (let alone in human beings), it seems that it is the patterns of information (or perhaps the patterns of energy to be more accurate) as well as the level of complexity or type of patterns that ultimately constitute that essence and identity. Now if it is reasonable to conclude that the patterns of information or energy that comprise any physical system aren’t equivalent to the physical constituent materials themselves, one could perhaps say that these patterns are a sort of “immaterial” attribute of a set of physical materials. This seems to be as close to the concept of an immaterial “soul” as a physicalist or materialist could concede exists, since, at the very least it involves a property of continuity and identity which somewhat transcends the physical materials themselves.