The zombie argument: objections Michael Lacewing

The argument It is conceivable that there are zombies. If it is conceivable that there are zombies, it is metaphysically possible that there are zombies. If it is metaphysically possible that there are zombies, then, contra physicalism, physical properties do not determine all mental properties. Therefore physicalism is false.

Zombies are not conceivable We cannot assume that physicalism is false. But if it is true, then zombies are not conceivable. A zombie is a physical duplicate of a person with phenomenal consciousness, but without phenomenal consciousness. A physical duplicate is a functional duplicate. Therefore, a zombie is a physical and functional duplicate of a person, but without phenomenal consciousness.

Zombies are not conceivable Phenomenal properties are physical properties realising particular functional roles. Therefore, a physical and functional duplicate of a person with consciousness has phenomenal consciousness. A physical and functional duplicate of a person with consciousness cannot both have and lack phenomenal consciousness. Therefore, zombies are inconceivable.

Objection We cannot assume that there is a complete physical and functional analysis of consciousness –Phenomenal properties of consciousness are ‘qualia’ – intrinsic, non-representational properties of experience We can know all about something’s physical structure and function without being able to explain consciousness – so we can conceive the same physical thing as having consciousness or not

Zombies are conceivable, but not possible This objection requires us to get clearer on possibility It is not an analytic truth that water is H 2 O. People can meaningfully ask ‘Is water H 2 O?’ It is conceivable that water is not H 2 O

Zombies are conceivable, but not possible However, water is H 2 O. And identity is necessary. –Identity is a relation between something and itself. Being H 2 O is what makes water what it is. –In every possible world in which water exists, water is H 2 O. It is possible that water in the oceans is fresh, that water never falls as rain, etc. But it isn’t possible for water not to be water, i.e. H 2 O.

Zombies are conceivable, but not possible If phenomenal properties just are certain physical and/or functional properties, then you can’t have these physical/functional properties without consciousness. So if physicalism is true, zombies are impossible. The second premise fails: just because zombies are conceivable, that doesn’t show they are possible.

Reply There is a disanalogy between water and phenomenal properties. The concept of ‘water’ is a concept of something with a particular structure and causal role; likewise H 2 O –Identical structure and causal role entails identical property

Reply Concepts of brain function are also concepts of structure and function But the concept of, e.g., ‘pain’ is a concept of how a sensation feels, not what it does –The essence of pain is its feeling So there is no reason to think that certain brain properties cannot exist without the feeling

Possibility and reality Suppose zombies are possible. How does that show that property dualism is true in the actual world, rather than some other possible world? Because identity is necessary. Phenomenal properties cannot be physical-functional properties in this world and not be the same properties in another world. –So if phenomenal properties are not physical- functional properties in some other possible world, they are not physical-functional properties in this world.

Possibility and reality Physicalism defends supervenience: any two things that are exactly alike in their physical properties cannot have different mental properties –Cp. aesthetic properties: two paintings that are physically identical must be aesthetically identical –Once all the physical properties are fixed, the aesthetic properties are fixed

Possibility and reality Likewise, once all the physical properties are fixed, the mental properties are fixed. The zombie argument attacks this claim – once the physical properties of our world are fixed, something further (e.g. an additional law of nature) is needed to fix the mental properties.