The philosophical zombie is one of the most famous thought experiments in the philosophy of consciousness.
Imagine a creature physically identical to a human being.
Its brain is identical.
Its nervous system is identical.
Its behaviour is identical.
Its internal functional organisation is identical.
It says that it is in pain when injured. It talks about colours, music and dreams. It writes philosophy. It insists that it is conscious.
But there is nothing it is like to be this creature.
There is no experience behind the behaviour.
It is, in the standard formulation, a philosophical zombie.
The point of the thought experiment is not that such creatures actually exist. The point is that they are supposed to be conceivable. If we can coherently conceive of a physically and functionally identical creature without consciousness, then physical and functional facts do not, on this argument, logically entail phenomenal facts.
The hard problem becomes unavoidable.
But there is something worth noticing about the experiment.
The zombie does not merely ask us to imagine an unusual creature.
It performs an operation.
The subtraction
The operation is remarkably simple.
Start with a human being.
Keep everything physical.
Keep everything functional.
Keep the behaviour.
Keep the causal organisation.
Keep the neural processes.
Then subtract consciousness.
What remains is the zombie.
The force of the argument depends upon the legitimacy of that subtraction.
But what does it mean to subtract consciousness while leaving everything else unchanged?
It means, at least for the purposes of the thought experiment, that consciousness can be specified independently of everything else that has been held constant.
And that is precisely what the experiment is supposed to establish.
There is something circularly suggestive about this.
We define the zombie by stipulating that the physical and functional facts remain exactly the same while the phenomenal facts differ.
We then conclude that the phenomenal facts are not entailed by the physical and functional facts.
But perhaps the thought experiment has not discovered an ontological separation.
Perhaps it has constructed a description in which the separation has already been made.
That does not make the argument trivial.
It makes it interesting.
The missing relations
Consider an organism rather than a description of an organism.
An organism is not merely a physical object with a set of functions attached to it.
It is a developing system whose organisation exists in continuous relation with its environment.
It regulates itself.
It distinguishes conditions that support its continued organisation from those that threaten it.
It acts.
It learns.
It changes.
Its history matters because its present organisation is the outcome of that history.
And its relations matter because what happens to the organism is significant for the organism.
None of this requires human language.
None of it requires reflective self-consciousness.
But it does suggest that the physical description of an organism is not exhausted by the list of physical properties we can abstract from it.
There is a difference between describing the organisation of a system and describing the relations in which that organisation exists.
The zombie argument holds the first constant.
But what happens if the relations themselves are constitutive of what the organism is?
Then the subtraction becomes less innocent.
The organism that never became
There is an even stranger feature of the zombie.
It is an adult.
A fully formed adult human duplicate simply appears, complete with the physical and functional organisation of an adult human being.
And then we ask whether it could lack consciousness.
But real organisms do not appear as adults.
They develop.
The adult organism is the outcome of an ontogenetic history extending from a beginning at which none of its mature capacities existed in their present form.
Human consciousness, in particular, develops alongside increasingly complex forms of social and semiotic organisation.
The child does not begin with an adult consciousness waiting to be expressed through language.
The capacities for meaning, reflection and symbolic thought develop.
The forms of consciousness available to the child change as the child's relations with other people and with language change.
So the zombie thought experiment performs another operation besides subtraction.
It freezes becoming.
It takes the endpoint of a developmental trajectory and treats that endpoint as though it were an independently specifiable state.
The zombie is not merely missing consciousness.
The zombie is missing becoming.
That may be a much more consequential absence than the thought experiment acknowledges.
From organism to object
There is therefore a subtle transformation taking place.
We begin with an organism.
We abstract its physical and functional organisation.
We hold that abstracted description fixed.
We then ask whether something called phenomenal consciousness could be different.
The organism has become an object of comparison.
Its history has disappeared.
Its developmental trajectory has disappeared.
Its participation in a world has been reduced to the properties represented in the description.
And the question becomes:
What else must be added?
Perhaps consciousness.
But perhaps what is missing is not another property.
Perhaps what is missing is the relation among the properties.
Or the history through which the organisation acquired its present form.
Or the biological value by which differences in the organism's world become differences that matter.
Or the social relations through which its capacities are transformed.
Or the semiotic processes through which experience becomes available for conscious construal.
The zombie thought experiment does not allow these possibilities to do much work because its rules have already declared them irrelevant.
That is why the operation deserves examination.
Conceivability and the observer
There is another complication.
Someone has to imagine the zombie.
And that someone is a conscious human being.
The philosopher constructs the zombie from within a human conceptual and semiotic world. The zombie is described as behaving like us, speaking like us, reporting experiences like us—and yet lacking what we call experience.
But the philosopher's access to the distinction is not neutral.
We do not encounter consciousness from outside consciousness.
We encounter organisms as participants in a world that already matters to us.
We do not first perceive raw experience and then, from a position outside it, attach the word red.
We learn to construe experience within a social semiotic system.
The very description of the zombie therefore depends upon capacities that the zombie is stipulated to lack.
This does not refute the thought experiment.
But it should make us cautious about what its apparent clarity means.
The zombie is extraordinarily easy to describe because we have already performed the abstractions necessary to make it describable.
What has the zombie shown?
Perhaps the zombie has shown that we cannot derive phenomenal experience from a purely physical-functional description.
That is certainly a possibility.
But there is another.
Perhaps it has shown something about descriptions rather than about the ultimate architecture of reality.
A description at one level of organisation may not contain everything that becomes explicit at another level.
We should not be surprised by this.
A description of a weather system in terms of atmospheric conditions does not contain, in isolation, everything that can be said about a climate.
A description of an organism's molecular composition does not by itself capture everything that matters about its life.
A description of a social practice in terms of individual physical movements does not exhaust its social significance.
The failure of one description to entail another does not necessarily mean that the phenomena described are ontologically independent.
It may mean that the relation between them is what matters.
And this brings us back to the possibility space.
The zombie argument seems to open a possibility: a physical duplicate without consciousness.
But perhaps it has first closed another possibility: that consciousness is inseparable from the developmental, biological, social and semiotic relations through which the organism becomes what it is.
The question is therefore not simply whether zombies are conceivable.
It is:
What had to disappear from the organism's history and relations before the zombie became conceivable?
That is the operation we need to examine next.
And once we do, the absent entity may turn out not to be consciousness at all.
It may be the organism.
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