Philosophical Zombie

philosophical zombie by mark hauge

A philosophical zombie or p-zombie in the philosophy of mind and perception is a hypothetical being that is indistinguishable from a normal human being except in that it lacks conscious experience, qualia, or sentience.

When a zombie is poked with a sharp object, for example, it does not feel any pain though it behaves exactly as if it does feel pain (it may say ‘ouch’ and recoil from the stimulus, or tell us that it is in intense pain).

The notion of a philosophical zombie is used mainly in thought experiments intended to support arguments (often called zombie arguments) against forms of physicalism such as materialism, behaviorism and functionalism. Physicalism is the idea that all aspects of human nature can be explained by physical means: specifically, all aspects of human nature and perception can be explained from a neurobiological standpoint. Since a zombie is physiologically indistinguishable from human beings its hypothetical possibility is an argument for a consciousness that is more than the sum of neurological pathways and brain states.

Though philosophical zombies are widely used in thought experiments, the detailed articulation of the concept is not always the same. P-zombies were introduced primarily to argue against specific types of physicalism such as behaviorism, according to which mental states exist solely as behavior: belief, desire, thought, consciousness, and so on, are simply certain kinds of behavior or tendencies towards behaviors. A p-zombie that is behaviorally indistinguishable from a normal human being but lacks conscious experiences is therefore not logically possible according to the behaviorist, so an appeal to the logical possibility of a p-zombie furnishes an argument that behaviorism is false. Behaviorists tend to respond that a p-zombie is not possible.

The unifying idea of the zombie is of a human that has no conscious experience, but one might distinguish various types of zombie used in different thought experiments as follows: A behavioral zombie that is behaviorally indistinguishable from a human. A neurological zombie that has a human brain and is generally physiologically indistinguishable from a human. And a soulless zombie that lacks a soul.

Zombie arguments often support lines of reasoning that aim to show that zombies are logically possible in order to support some form of dualism — in this case the view that the world includes two kinds of substance (or perhaps two kinds of property); the mental and the physical. According to physicalism, physical facts determine all other facts. Since any fact other than that of consciousness may be held to be the same for a p-zombie and a normal conscious human, it follows that physicalism must hold that p-zombies are either not possible or are the same as normal humans.

The zombie argument is a version of general modal arguments against physicalism such as that of Saul Kripke against that kind of physicalism known as type-identity theory. Further such arguments were notably advanced in the 1970s by Thomas Nagel and Robert Kirk but the general argument was most famously developed in detail by David Chalmers in ‘The Conscious Mind’ (1996). According to Chalmers one can coherently conceive of an entire zombie world, a world physically indistinguishable from this world but entirely lacking conscious experience. The counterpart of every conscious being in our world would be a p-zombie. Since such a world is conceivable, Chalmers claims, it is logically possible, which is all the argument requires. Chalmers states: ‘Zombies are probably not naturally possible: they probably cannot exist in our world, with its laws of nature.’

The outline structure of Chalmers’ version of the zombie argument is as follows;

  • According to physicalism all that exists in our world (including consciousness) is physical.
  • Thus, if physicalism is true, a logically-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. In particular conscious experience must exist in such a possible world.
  • In fact we can conceive of a world physically indistinguishable from our world but in which there is no consciousness (a zombie world) and we can not see why it is not logically possible.
  • Therefore, physicalism is false.

Some philosophers maintain that a possibility stronger than logical possibility is required and that, while a zombie world is logically possible (that is, there is no logical contradiction in any full description of the scenario), such a weak notion is not relevant in the analysis of a metaphysical thesis such as physicalism.

Another response is denial of the idea that qualia and related phenomenal notions of the mind are in the first place coherent concepts. Daniel Dennett and others argue that while consciousness and subjective experience exist in some sense, they are not as the zombie argument proponent claims. The experience of pain, for example, is not something that can be stripped off a person’s mental life without bringing about any behavioral or physiological differences. Dennett believes that consciousness is a complex series of functions and ideas. If we all can have these experiences the idea of the p-zombie is meaningless.

He coined the term zimboes (p-zombies that have second-order beliefs) to argue that the idea of a p-zombie is incoherent; ‘Zimboes ‘think’ they are conscious, ‘think’ they have qualia, ‘think’ they suffer pains – they are just ‘wrong’ (according to this lamentable tradition), in ways that neither they nor we could ever discover!’ As p-zombies in an observed world would be indistinguishable from the observer (and therefore non-existent as a class) one must either believe that anyone, including oneself, might be a zombie or else that no one may be a zombie. One’s own conviction about being (or not being) a zombie is a product of the physical world and is no different from anyone else’s.

The zombie argument is difficult to assess because it brings to light fundamental disagreements about the method and scope of philosophy itself and the nature and abilities of conceptual analysis. Proponents of the zombie argument may think that conceptual analysis is a central part of (if not the only part of) philosophy and that it certainly can do a great deal of philosophical work. However others, such as Dennett, Paul Churchland and W.V.O. Quine, have fundamentally different views. For this reason, discussion of the zombie argument remains vigorous in philosophy.

Frank Jackson’s ‘Mary’s room’ argument is based around a hypothetical scientist, Mary, who is forced to view the world through a black-and-white television screen in a black and white room. Mary is a brilliant scientist who knows everything about the neurobiology of vision. Even though Mary knows everything about color and its perception (e.g. what combination of wavelengths makes the sky seem blue) she has never seen color. If Mary is released from this room and experiences color for the first time, will she learn anything new?

‘Swampman’ is an imaginary character introduced by Donald Davidson. If Davidson goes hiking in a swamp and is struck and killed by a lightning bolt while nearby another lightning bolt spontaneously rearranges a bunch of molecules so that, entirely by coincidence, they take on exactly the same form that Davidson’s body had at the moment of his untimely death then this being, ‘Swampman’, has a brain structurally identical to that which Davidson had and will thus presumably behave exactly like Davidson. He will return to Davidson’s office and write the same essays he would have written, recognise all of his friends and family and so forth.

John Searle’s ‘Chinese Room’ argument deals with the nature of artificial intelligence: it imagines a room in which a conversation is held by means of written Chinese characters that the subject cannot actually read, but is able to manipulate meaningfully using a set of algorithms. Searle holds that a program cannot give a computer a ‘mind’ or ‘understanding,’ regardless of how intelligently it may make it behave.

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