In 1994 the philosopher David Chalmers raised questions about consciousness which ignited a zombie apocalypse.
These weren’t questions no one had asked before. These were questions that rattled the established orthodoxy. They challenged the complacent modern assumption that science had settled all such questions.
Many people assume it’s no longer an open question whether there is a soul separate from the body which could survive death. The modern mythology says science exorcised that ghost from the machine long ago. It’s assumed everything worth explaining would eventually be explained by science.
Then Chalmers released the philosophical zombies, and the war began.
What is a philosophical zombie?
Rather than the blood-stained, reanimated corpse of horror films, a philosophical zombie is less frightening. It’s an explanatory nightmare.
Imagine you meet your doppelganger. Someone physically identical to you, atom for atom. The only difference is the doppelganger has no inner consciousness. They look happy or sad, they even tell you of their hopes and dreams.
But there is nothing more than physical processes moving in response to physical causes. Their lips move and sounds which are meaningful to you come out, but they experience nothing at all.
From the outside you are identical. But from the inside the zombie is a hollow imitation. That is a philosophical zombie. The physical structure, functions and behavior are identical, but there is no consciousness.
What exactly is the missing ingredient?
Consciousness is an ambiguous term, sometimes consciousness can mean the difference between being asleep and being awake. Or having the ability to react to information, focus attention and other similar cognitive abilities. Chalmers calls these type of brain functions the easy problems of consciousness. He contrasts these easy problems with the hard problem. He says,
“The really hard problem of consciousness is the problem of experience. When we think and perceive, there is a whir of information processing, but there is also a subjective aspect.” ¹
Philosophers call this subjective experience qualia, or “what it is like”. Experiential states are those states there is something it is like to be in them. There is something it is like to taste a lemon, which is different to what it is like to do your income taxes, or have a toothache, listen to fingernails scraping down a blackboard, be envious, or have a memory on the tip of your tongue.
The rich and distinctive inner feel of all those experiences is very different. That inner world is so familiar, so fundamental to our existence we rarely question it or notice how extraordinary consciousness is. It’s this aspect of consciousness, the inner feel or conscious experience, that the zombie lacks.
Why is it a hard problem?
The conceptual distinction behind the easy problems of consciousness and the hard problem shows the challenge faced by a science of consciousness.
“The easy problems are easy precisely because they concern the explanation of cognitive abilities and functions. To explain a cognitive function, we need only specify a mechanism that can perform the function. The methods of cognitive science are well suited for this sort of explanation and so are well suited to the easy problems of consciousness.”²
To explain the difference between the states of asleep and awake only requires a description of brain processes responsible for the contrasting behavior. All it means for a system to be awake is for the system to be receptive to information from the environment and use this information to direct its behavior. The state we call awake is a functional state.
To explain a functional state requires specifying a mechanism that performs the function. Scientific reductionist explanations work on the principle that we can understand all phenomena by explaining their elementary parts. A description of the structure, the functions and the motion and interaction of those parts is all we need to completely explain any phenomena.
But when it comes to conscious experience, this sort of reductive explanation fails. Even if we have a complete explanation of all structure and function, there will always be a further unanswered question: Why is this function accompanied by experience? Why is there an inner feel?
No reference to mechanism can answer that question. Which means there can be no reductionist explanation.
Isn’t it enough to explain the functions?
All this may seem like an intellectual chimera, everyone knows zombies aren’t real so does it matter? Isn’t it enough to explain how the brain works?
It matters for the philosophy of physicalism.
For the physicalist it’s an explanatory nightmare. The stakes are high. If there can’t be a scientific explanation of conscious experience, this shows physicalism is false.
Physicalism is the claim the only type of things which exist are physical things. What physical means can be understood in different ways and there is some wiggle room available.
But generally speaking, physicalism says everything which exists can be explained by the laws of physics; or is fully reducible to things that can be explained by the laws of physics.
If science is restricted to reductive explanations, but no such explanation can include conscious experience, then science cannot explain it. Many people take it for granted that cognitive science will eventually explain consciousness. Chalmers’ distinction put the truth of that in jeopardy.
Science can explain the easy problems. Easy is an understatement, the easy problems will take many years of advanced research. But in principle there is no real difficulty. They’re all the sort of problems we expect science to solve because they deal with structure and functions.
The hard problem is different. Hard is also an understatement, it’s a euphemism. It really means impossible.
Conscious experience is a phenomena which in principle science can’t explain.
Confronting the nemesis of the scientific method — why is anyone surprised?
When we consider what the scientific method consists of, this apocalypse is predictable.
The philosopher Thomas Nagel argues that the scientific method creates the mind body problem. Science is a method of inquiry which intentionally excludes certain phenomena from explanations.
The excluded features are first person phenomena. Science deals only in quantitative objective properties, third-person properties. All first-person qualitative phenomena are swept out of sight, under the category of the mind.
The observed nature of the world itself didn’t demand the scientific method, it was a stipulated demand, only certain aspects of the world could be included in scientific explanations.
So it shouldn’t be a surprise that when science confronts the fundamental properties of the mind, it finds itself incapable of breaching the divide.
Because it intentionally created the divide.
Scientific explanations create the hard problem of consciousness. Stipulating that only objective third-person features of matter are acceptable as scientific explanations, intentionally excludes first-person properties.
By describing red in objective features as wavelengths of electromagnetic radiation we’ve stipulated science must exclude the experience of seeing red from any explanation.
The physicalist trilemma
The mind body problem lies in the intersection of three observations, creating a trilemma –
Consciousness is non-physical.
The physical world is causally closed, all physical effects have physical causes.
Consciousness is causally effective. Mind affects body.
All three can’t be true simultaneously, so we must deny one to avoid logical contradiction.
What is the solution?
The physicalist must deny the first observation, they have no choice. If it’s true that consciousness is non-physical, then not everything is physical, and physicalism is false.
The physicalist must accept the second, the causal closure of the physical. If causal closure is false then not every physical effect has a physical cause, and again physicalism is false.
Denying the third means consciousness doesn’t have any causal power, despite appearances to the contrary. When you move your body to the fridge in response to a desire for a snack, or take medication in response to pain, or lock the doors due to a fear of burglars, there is no causal connection between those conscious states and the physical effects of your body moving.
This view isn’t fatal to the physicalist theory, but it puts it on critical life support. Our mental states cause actions which move matter constantly, giving us a lot of evidence it’s true. Any arguments those powers are illusory will need to be stronger than our confidence our conscious states cause our bodies to move.
Which is why the most popular option for the physicalist is to deny the first observation that consciousness is non-physical.
Denying consciousness is non-physical
Physicalists have two broad options. They can agree that consciousness has non-physical properties, but argue those properties are fully reducible to physical properties like brain processes. This results in a property dualism, consciousness is a property of brains like liquidity is a property of water.
This option avoids the immediate danger of consciousness being non-physical, but it creates more problems. Not only do they still need to confront the hard problem of showing how physical mechanisms produce non-physical properties, but they also have the problem of causal over-determination and top-down causation.
If property dualism is true, those non-physical properties have causal power. But this means we have causal over-determination. We have the physical causes (whatever physical things consciousness reduces to) and the non-physical properties as causes.
My fear of burglars does cause me to move my body, but fear isn’t a physical property. Even if fear is shown to be reducible to a brain state, now both the brain state and the experiential state of fear are causes. Our causal explanations are over-determined.
It also means the causation proceeds from the non-physical properties to the physical, from the top down. But that violates causal closure which says all physical effects have physical causes.
A second option, which is a minority view among physicalists, is to deny there is any problem to be explained. They argue that once we’ve explained all the functions and mechanisms, there is nothing left to explain. That we think there is a problem is only a result of ignorance, as was the case when it was proposed life couldn’t be explained without theorizing the existence of a vital force (elan vital).
However, this line of argument ignores the unique nature of consciousness. Consciousness isn’t an explanatory postulate, something like elan vital that we theorize exists to explain some other thing (life). Conscious experience is the thing to be explained. So it’s not possible to eliminate the phenomena in this way.
The end of physicalism as we know it?
Confronting the hard problem of consciousness logically leads to an expansion of physicalist ontology. Consciousness must be added to the fundamental constituents of reality like space or time.
These are fundamental properties that are elementary and basic, they aren’t themselves explained but are the explanatory framework which contains the explanations.
It isn’t our conception of consciousness that needs to change, it’s our conception of matter. The mechanistic philosophy views matter as an insentient machine.
This arose from the habit of seeing matter that way because it was practical for scientific investigation. From that way of seeing the world, many came to think the world was, in fact, like that. A naturalist method morphed into a metaphysics.
The new conception of the physical world found in quantum mechanics and the participatory role the conscious observer plays, has long ago superseded the mechanical conception of nature. Yet we still labor under the mechanistic paradigm from the age of Newtonian physics.
All these problems are only problems for the physicalist. Alternative metaphysics, like idealism, substance dualism or panpsychism all avoid the hard problem by denying causal closure. They accept the observation that consciousness is non-physical, and it’s causally effective, which means causal closure must be false.
Unlike the observations of consciousness and its causal powers, causal closure isn’t based on observations of the world. It’s a metaphysical commitment. Physicalism is confronting a problem created by its philosophical commitments being in conflict with our observations of the world.
The conceptions of the world both science and philosophy have led us to, are starting to look a lot like the spiritual conceptions of our ancestors. Maybe modern humans aren’t such clever apes after all.
All quotes from David Chalmers, The Character of Consciousness
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