Philosophical zombie

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Saint Denis of Paris, famous philosophical zombie.

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A philosophical zombie or p-zombie is a hypothetical being that is physically indistinguishable from a human being in both appearance and behavior, but lacks conscious experiences. It's a concept related to the problem of other minds.

There are philosophers who actually take this notion seriously and consider that the p-zombie thought experiment is sufficient to prove some kind of dualism. Others are less inclined to state the thought experiment "proves" dualism, but take it seriously as illustrative of the hard problem of consciousness and why it requires a serious solution.

History

The concept of a machine acting like a human being without having consciousness dates back to Rene Descartes (1596-1650). Robert Kirk introduced the term "zombie" within a philosophical context in 1974, and Daniel Dennett popularized it in 1991. At some stage, a person or persons unknown expanded the term "zombie" to "philosophical zombie" — to distinguish the philosophical concept from the zombies of the Haitian voodoo tradition and from the zombies in monster movies. This was then abbreviated to "p-zombie".

Types

Taxonomists of the p-zombie phenomenon can distinguish several different kinds of p-zombies, depending on how they are indistinguishable from humans and what specific human quality they lack.

• A p-zombie might just be behaviorally indistinguishable from a human being. Dissecting such a zombie, we might find that it differs completely from a real human being.
• A p-zombie might be functionally equivalent with human beings. That is, such a p-zombie might have a brain made of wires and transistors, but those wires and transistors would correspond to the axons and neurons of a human brain, and it would be possible to map one to the other.
• A p-zombie may be in every way equivalent to a human being, but only be simulating the exact way a human would react without consciously experiencing events.
• A p-zombie might also be physically identical with a human being. Assuming that such a p-zombie is different from a human being would require some kind of dualism or idealism.

Furthermore, there are several different qualities a p-zombie might lack. Often, a p-zombie is assumed to lack qualia, but other possiblly missing qualities are intentionality, free will, consciousness, or a soul.

Chalmers' p-zombies

Maybe the most important presentation of p-zombies in contemporary philosophy was made by David Chalmers in the 1990s. Chalmers's core argument is roughly:

P1: P-zombies are conceivable.

P2: If p-zombies are conceivable, then they are metaphysically possible.

C1: So, p-zombies are metaphysically possible.

P3: If p-zombies are metaphysically possible, then physicalism is false.

C2: So, physicalism is false.

Philosophers' objections tend to concentrate on the first two premises, and Chalmers goes to some lengths to describe a notion of conceivability that secures metaphysical possibility and show that p-zombies fall under this notion. Importantly, the argument does not depend on the physical possibility of p-zombies — in fact, Chalmers does not believe that p-zombies could exist in the actual world. There is no suggestion that any actual person might secretly be a p-zombie. Rather, what Chalmers argues is that, for some (specialized) sense of "could", it could have been the case that the world was physically identical to the actual world and yet there be no conscious experience.

Chalmers' zombie argument is made as part of an argument for a kind of property dualism, which he describes as involving "properties of an individual that are not entailed by the physical properties of that individual, although they may depend lawfully on those properties". This is a weaker version of dualism than the better known substance dualism familiar to many from Descartes, who posited a distinct mental substance. Chalmers goes on to argue that the dualism he advocates is naturalistic, compatible with contemporary scientific knowledge.

Objections

One prominent objection, made by Daniel Dennett among others, is that zombies are not even conceivable. Dennett argues that proponents of the zombie argument fail to imagine zombies in adequate detail because neural functions are highly sensitive to fine structures; he extends this to argue that zombie intuitions are self-undermining. Others have argued that the conceivability of p-zombies would entail that conscious experiences have no causal effects, and that this is implausible.

The second major category of objections are those against the inference from conceivability to possibility. Some philosophers have argued that the conceivability of zombies does not entail the relevant kind of possibility. Two grounds for this objection are the gap between the epistemic premise of conceivability and the metaphysical conclusion of Chalmers' argument and the inference from features of our conceptual understanding of conscious experience to the existence of real non-physical properties in the world.

Popular Argument

Outside the academy, a number of popular variants of the zombie argument have developed. They generally do not carry through the conceptual distinctions made by Chalmers. Often, p-zombies are presented as things which might exist in the actual world. This is sometimes accompanied by the suggestion that somebody you know might actually be a zombie. Such claims are relatively strong, and so open to distinctive objections.

Objections

A common objection is that the concept does not make sense without assuming dualism in the first place, thus the idea is begging the question.

It does make for an interesting enough thought experiment, where you can ask how you'd tell p-zombies apart from "real" humans, even extending to how you could tell that you, yes you, aren't a p-zombie at all. Indeed, if there is no answer, then the soul is unfalsifiable by the limits imposed on it by this thought experiment itself and so doesn't exist or have any bearing on our lives in any meaningful way — belief in it wouldn't even be trivial. If, on the other hand, an observable difference was proposed, the soul would cease to be supernatural, and again, the thought experiment that set out to prove the soul exists in fact disproves it, or at least certain attributes of it.

The other objection is against the conceptual existence of p-zombies, as thinking you can conceive of something doesn't mean the universe gives a shit. Religious apologists have tried that one already.

It has also been pointed out that the arguments in favor of p-zombies are eerily similar to those used in order to justify slavery and oppression in eras past. In the future, the philosophical zombie argument could be uncritically applied to any robot even if one would otherwise have to conclude it was even more intelligent, sentient, and conscious than your typical human (some science fiction explores exactly this).

Conclusions

The concept of a p-zombie is a two-edged sword. On the one hand, if it is possible to show that p-zombies can exist, then the theory of eliminative materialism is in trouble, since it would seem that there are phenomena which can't be reduced to strictly materialistic causes. Proving that p-zombies can exist is impossible unless we can define them. Could an entity lacking consciousness be indistinguishable in all material respects from a conscious human being? Since we do not know what causes consciousness, all we can currently say given present scientific knowledge is that we don't know. Furthermore, there is sometimes a confusion between whether practically or theoretically detectable differences are meant; if consciousness has a material basis, there are certainly material differences between conscious and unconscious beings, regardless of whether or not scientists can detect these differences using the current means of measurement at their disposal.

On the other hand, p-zombies can be used to attempt to show that several concepts like the irreducibility of qualia don't make sense, since they would allow the existence of p-zombies, without any means to distinguish them from ordinary people. Some have even argued that it then would be impossible to know if oneself is or is not a p-zombie. The third type of p-zombie, indeed, might be indistinguishable by any means, considering that there is no physical evidence for the existence of a soul.

It's also a good way to justify callous treatment of your fellow human beings. People will still heavily dislike you for it.

See also

• Chinese room
• NPC — an alt-right term for demeaning the left-wing
• Solipsism, the belief that everyone on Earth other than you is a p-zombie.
• Turing test
• Zombies

External links

• The p-zombie movie, LessWrong - "I'm Daniel Dennett, bitches!"
• The zombification of philosophy (of mind), Massimo Pigliucci