A philosophical zombie (also called a p-zombie) is, in philosophy, a thought experiment that plays into our ideas about consciousness. Basically, a p-zombie is a person who looks and acts like any other person, but who doesn’t have consciousness. There are two different versions of a p-zombie:
The first version is only a functional p-zombie. This is a zombie that looks and acts identically to any human, but that internally is not identical (the physical construct is different). You can think of such a p-zombie as a cyborg that from the outside looks and acts identically to a human (acts based on input and data received), in which the program/cyborg outputs exactly what a person might have done, but never truly experiences consciousness like a person does. The point about this type of zombie is that it is not physically identical to a human.
The next version is both a functional and physically identical p-zombie. In other words, it’s as if we were to duplicate your entire physical structure, without the consciousness existing, yet the zombie would still do everything you would have done through only the physical processing but without the consciousness as a part of such.
It’s this second version that this article will be about, which happens to be the more common version when philosophers talk about “philosophical zombies”. From here on out when I address a philosophical zombie or p-zombie, I’m talking about a zombie that is both physically and functionally identical to a conscious human, but who does not experience consciously. So though it may pick up a rose and smell it, it doesn’t actually experience the redness of the rose, the fragrant odor that the rose gives off, and so on. ..in some consciously aware way. That is not to say the eyes and brain don’t detect that only a certain wavelength of light is bouncing off the rose hitting the eye, which may change the structure of the brain, only that the qualia of redness isn’t in any way experienced in some sort of internal subjective screen like we would normally experience.
A large part of the discussion surrounding such stems to whether or not a p-zombie is “conceivable”, which for most just means it isn’t something that is logically ruled out. In other words, if a priori there is no contradiction, such is considered “conceivable” – that, conceivably, there could be a p-zombie, or even many p-zombies, all walking around and we wouldn’t even know it (even if we were to look at brain scans as such would be identical).
Some think that the very conceivability of p-zombies goes against physicalism, that being everything, including conscious experience, is part of physical processes. David Chalmers developed such an argument. According to him, we can conceive of a world physically identical to and indistinguishable from our own, with no conscious creatures (only p-zombies). Here is the gist of his argument:
- The p-zombie world is conceivable, therefore it is metaphysically possible.
- Per physicalism, all that exists in our world is physical (which includes consciousness).
- If physicalism is true, a metaphysically possible world in which all physical facts are the same as those of the actual world must contain everything that exists in our actual world, including consciousness.
- Since such a p-zombie world is metaphysically possible, physicalism is false.
Though this logic is valid, meaning the conclusion follows from the premises, it isn’t a sound argument. The largest mistake is with the premise “The p-zombie world is conceivable, therefore it is metaphysically possible”. It’s only conceivable in that we can (logically) conceive of physicalism being false, not that such implies it actually is false. If physicalism is true, then it is neither metaphysically possible, nor is it conceivable. In other words, if we reverse the premises, our argument can be equally as valid:
- Physicalism is true, therefore the p-zombie world is metaphyically impossible.
- If the p-zombie world is metaphyically impossible, it’s logically inconceivable.
- P-zombie worlds are logically inconceivable.
The error here should be obvious, in both cases we are question begging with the first premise. The very idea of “conceivability” of such a world assumes that we are conceiving consciousness to be something “outside of” the physical to begin with. And likewise if we assume physicalism to be true, such assumes the p-zombie world is inconceivable. The problem is, we can address conceivability in a more modal fashion, meaning “if physicalism is false, the p-zombie world is conceivable” and “if physicalism is true, the zombie universe is inconceviable”, but this does not imply conceivability in both worlds.
If the a priori logic isn’t your cup of tea, let’s get a little into the a posteriori evidence instead. That, I’d suggest, is where we need to go when we are addressing whether or not consciousness is a part of the very physical processing, or if it is just “going on in the sidelines”.
A past article of mine gives some (hardly the bulk of) evidence that “strongly points” to consciousness being an output of brain states:
Consciousness – An Output of Brain States
Those are only a few examples. A more recent example was the ability to turn off and on conscious states in an epileptic woman by stimulating a single region of the brain with electrical impulses. There are also many other things going on in neuroscience, such as studying how brain activity differs for conscious awareness compared to unawareness. Neuroscientists have also used transcranial magnetic stimulation and intracranial electrodes to directly create perceptions in surgery patients.
Some might look at the evidence that conscious experience is an output of brain states as strictly correlation rather than causation. And as we all know, correlation doesn’t necessarily imply causation. But there comes a point when we have mounds upon mounds of correlated evidence, and none that doesn’t have the correlation, in which it becomes rationally undeniable in regards to causation. We might as well say that the Earth heating up is “only” correlated to the rays of the sun, we can’t infer that there is actual causation there. This pretty much stems to all empirical evidence. This is fine (well not really) if one wants to take the whole “problem of induction” to this level, as long as they are consistent across the board.
I’d suggest, however, that the neuroscientific and behavioral evidence is more than sufficient to conclude a great likelihood that consciousness isn’t something separate from the physical.
Many neuroscientists don’t see consciousness as simply an output of brain processing (an epiphenomenon of brains), but also as playing important functional roles. For example, in his book “Consciousness and the Brain: Deciphering How the Brain Codes Our Thoughts“ (2014), Stanislas Dehaene sees consciousness as being important for collapsing many lower-level probability assessments into one perception, for creating lasting thoughts that remain in memory for a later time, for multi-step reasoning and computations, for sharing information with others through language and non-verbal signals, and for optimal judgement.
Dehaene also explains some of the different “signatures” of conscious thought, such as amplified brain activity in many regions (which is much greater than unconscious workings that “peters out” rather than gaining momentum like conscious workings), ignition of a late P3 wave when a word is consciously seen, an increase in gamma waves, and the brain doing an information sync with the rest of the brain’s “web”.
I agree with Dehaene that consciousness plays important functional roles. And though conscious processes stem from unconscious processes causally (of course), those conscious process are just as relevant as the unconscious processes for the output of the next configuration of the brain. Some may think that it’s simply the physical configuration that leads to the next, and I agree with them. But I think consciousness is a property of physical configurations, and therefore not something that is placed to the side of what is physical, just as we wouldn’t place the property of wetness outside of what constitutes water at a certain temperature. And those properties matter for the next causal happening (if it wasn’t for the property, the output would be different).
Take the placebo effect as an example. We are given a pill and informed that the pill will help our symptoms. As we do, we notice those symptoms decrease. Later, we are told that the pill was just a placebo, basically a sugar pill. So what’s happening here? The information that is given to us adjusts the configuration in our brain to the point of a conscious output. That conscious output is the belief that the pill will help our symptoms. But it’s that very belief that plays with our psychology and reconfigures our mind in a way that lessens the symptoms we are having. If it wasn’t for the actual conscious belief, but simply the correlated configuration of atoms without the production of such conscious belief, there would be nothing to trick the mind. Rather, it’s the experience that is a property of those configurations of atoms that causally play back into the system.
Most evolutionary biologists would suggest that conscious experience has an effect on our behavior, which is often an evolutionary advantage. The ability to learn through the painful experience felt of placing your hand in fire or on a thorn leads to the avoidance of such. This is why those people who have congenital insensitivity to pain are more prone to greater injury. They don’t have the conscious output that tells them they are injured, allowing them to keep doing the action that causes even more injury. A p-zombie would be missing this mechanism of avoidance, and such wouldn’t be replaced by another if the p-zombie is physically identical to a conscious person.
These ideas move us away from reductionism into a more downward causal way of thinking about physics and consciousness. Parts create wholes with properties that play into the very parts. The properties of structures are just as important to the physical playout as the individual parts that make them up. This is, for the most part, a given in science. The buoyancy of a swan in water isn’t from one specific particle that makes it up, but due to the entirety of the very specific structure that all of the particles derive. When it comes to consciousness, however, people have a tendency to think it something “outside of physics” special, simply because of its uniqueness and our difficulties measuring it due to it’s internally observed nature (which may change in the future).
As soon as we recognize that physical states and consciousness truly aren’t something that can be “separated” from each other, we need to recognize that the p-zombie world is inconceivable, because if the p-zombies have the same physical components working in the same ways, they must also have the same conscious experience playing out. From a physicalist perspective, separating consciousness from the physical structure of the brain playing out is like separating “wetness” from the physical structure of the water, or roundness from the physical structure of a wheel rolling down a hill. It doesn’t make a whole lot of sense.
Now if we are talking about a functional but not identical p-zombie, that’s an entirely different discussion. For that, the questions remain regarding how advanced we can make artificial intelligence, and how realistic we can make such appear without an actual consciousness showing up. Or perhaps at some point those machines will start to experience as well. After-all, if consciousness is the play-out of our biological “hardware”, the biological component may be unnecessary.
All of that said, the topic of consciousness and the “hard problem” is a very large topic, with many different ideas swirling around many different minds. And though I think there is no evidence for mind-body dualism (the mind being something that is in some way separate from the body) and much evidence pointing to mind being an aspect of the physical body’s configuration, and though I think consciousness, at least for various biological creatures, plays an important causally functional role, I still seek more conclusive evidence in either direction. In the meantime I’m swayed over to the side that physically identical p-zombies are not conceivable.
How about you? Do you think p-zombies (of the physically identical sort) are conceivable?
'Trick Slattery
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2 Responses to “Philosophical Zombies? Inconceivable!”
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Conceivability has always just struck me as such a strange guide to metaphysical possibility. We can be (and often are) mistaken about what we can and can’t “really conceive of,” and even if that weren’t the case I really struggle to see why logical coherence should be the arbiter of metaphysical possibility. Not implying a contradiction is a ridiculously low bar to meet, and it seems like we should make stronger demands of our metaphysics. I’ve never been a big fan of Chalmers.
If zombies existed there would have to be some difference even if it was so subtle we couldn’t measure it with current scientific knowledge and technology and this is true whatever metaphysics one subscribes to.
In a materialistic universe the zombie brain would not produce consciousness while the true human brain would and if all mental phenomena are caused by physical phenomena, the two types of brains would be doing something different or be structured differently.
But even if dualism is true, the (hypothetical) separate mind would interact with the brain and thus there would have to be a reason why some brains have no true minds paired with them and there would be some potentially observable lack of brain/mind interaction in zombies.